TRANSACTIONS 


OF  THE 


AMERICAN  SOCIETY 


op 


CIVIL  ENGINEERS 

(INSTITUTED  1852) 


VOL.  LXVII 

JUNE,  1910 


Edited  by  the  Secretary,  under  the  direction  of  the  Committee  on  Publications. 
Reprints  from  this  publication,  which  is  copyrighted,  may  be  made  on  condition  that 
the  full  title  of  Paper,  name  of  Author,  and  page  reference  are  given. 


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PUBLISHED    BY    THE  SOCIETY 


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It 


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Entered  according  to  Act  of  Congress,  in  the  year  1S10,  by  the  American  Society  ok 
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Note.—  This  Society  is  not  responsible,  as  n  body,  hw  the  facts  and  opinions  advanced  in 

any  of  its  publications. 


CO  NT K  NTS 


PAPERS 


NO.  Y  PAGE 

1148   NOTES  ON  THE  REPLACING  OF  THE  SUPERSTRUCTURE  OF  THE  HAR- 
LEM RIVER  SHIP  CANAL  BRIDGE. 

By  Horace  J.  Howe   i 

Discussion: 

By  Lincoln  Bush   23 

Martin  Gay     24 

St.  John  Clarke    20 

Theodore  Belzner   27 

Frank  W.  Skinner   28 

Horace  J.  Howe   SO 

1141    PRECARIOUS  EXPEDIENTS  IN  ENGINEERING  PRACTICE. 

By  John  Hawkesworth   32 

Discussion: 

By  Eugene  W.  Stern   46 

W.  W.  Crosby   48 

J.  S.  Branne   50 

Andrews  Allen   52 

Guy  B.  Waite   55 

J.  H.  Gandolfo   57 

John  Hawkesworth   59 

1145   WATER  SUPPLY  FOR  THE  LOCK  CANAL  AT  PANAMA. 

By  Julio  F.  Sorzano   01 

Discussion: 

By  C.  E.  Grunsky    «.)1 

H.  F.  Hodges   96 

Theodore  Paschke   100 

Allen  Hazen   108 

CM.  Saville   112 

Julio  F.  Sorzano   133 

1140   THE  IMPROVED  WATER  AND  SEWAGE  WORKS  OF  COLUMBUS,  OHIO. 

By  John  H.  Gregory   206 

Discussion: 

By  Joseph  W.  Ellms   324 

Julian  Griggs  ,   325 

C-E.  A.  Winslow   328 

R.  D.  Scott  and  R.  F.  McDowell   330 

Samuel  Tobias  Wagner  ,   334 

J.  Corbett   385 

W.  R.  Copeland   387 

W.  A.  Sperry   342 

J.  W.  Sale   845 

C.  P.  Hoover   854 

C.  B.  Hoover   359 

A.  Elliott  Kimberly   379 


IV 


No.  PJL0I 

1146   Discussion  (Continued): 

Samuel  Rideal   388 

Alexander  Potter   390 

Gilbert  Fowler   394 

William  Gavin  Taylor   397 

Allen  Hazen   399 

William  B.  Fuller   400 

Emil  Kuichling   402 

Langdon  Pearse   406 

Rudolph  Hering   407 

George  A.  Johnson   415 

George  W.  Fuller   419 

John  H.  Gregory   426 

1117    AGREEMENTS  FOR  BUILDING  CONTRACTS. 

By  William  B.  Bamford   438 

Discussion: 

By  Norman  R.  McLure   478 

William  V.  Polleys   479 

Charles  H.  Higgins   481 

W.  G.  Wilkins   483 

William  A.  Boring   486 

J.  C.  Wait   488 

W.  L.  Bowman   491 

Charles  A.  Ruggles   493 

Oscar  Lowinson   496 

E.  T.  Thurston,  Jr   497 

John  Mason  Brown   502 

J.  A.  L.  Waddell   BIO 

DeWitt  V.  Moore   515 

Leslie  H.  Allen   520 

William  B.  Bamford   525 

His    UNDERPINNING  THE  CAMBRIDGE  BUILDING,  NEW  YORK  CITY. 

By  T.  Kennard  Thomson   553 

Discussion: 

By  Henry  (>orton  Opdycke   BH 

E.  A.  Yates   566 

Ogden  Merrill   567 

Oscar  Lowinson   568 

J.  C.  Meem   569 

T.  Kennard  Thomson   570 

1149   THE  EFFECT  OF  ALKALI  ON  CONCRETE. 

By  Georjje  Gray  Anderson   572 

Discussion: 

By  R.  A.  Hart   587 

Rudolph  Hering   592 

Richard  L.  Humphrey   598 

George  F.  Morse   601 

Richard  H.  Gaines   602 

Thomas  H.  Means   606 

F.  E.  Robertson   608 

Philo  EL  Bates   608 

E.  P.  (Joodrich   611 

W.  E.  Belknap   612 

( J  eorgk  (»ray  Anderson   617 


V 

MEMOIRS  OF   DECEASED  MEMBERS 

PA(iK 


Hknry  Furlong  Baldwin.  M.  Am.  Soc.  C.  E   621 

Clifford  Buxton,  M.  Am.  Soc.  C.  E   623 

Wilson  Crosby,  M.  Am.  Soc.  C.  E   62."> 

John  Hall  Emigh,  M.  Am.  Soc.  C.  E   62K 

Henry  Cyprian  Humphrey,  M.  Am.  Soc.  C.  E   880 

Henry  Maynadier  Steele,  M.  Am.  Soc.  C.  E   681 

John  Joseph  Horan,  Assoc.  M.  Am.  Soc.  C.  E   684 


PLATES 


PLATE  PAPER  PAGE 

\.  South  Span.  Harlem  Ship  Canal  Bridere,  Being  Made  Ready  for 

Final  Move,  and  North  Span  at  Beginning  of  Erection   1143  5 

IF.           Old  Draw-Span  Ready  for  Final  Move,  and  Old  and  New  Draw- 
Spans   1148  9 

HI.  New  Draw-Span  in  Readiness  to  Move,  and  Present  Harlem  Ship  V 

Canal  Bridge   1143  11 

IV.  Coteau  Bridge,  and  Brunot  Island  Bridge  on  Falsework  Floating  on 

Barges   1113  29,^" 

V.  Topographical  Map,  Showing  Ridge  at  Escoval,  Canal  Zone   1145  120 

VI.  Map  of  Part  of  Lake  Gatun,  Canal  Zone   1145  165 

VII.  Views  of  Dam,  and  of  Scioto  River  Pumping  Station  and  Water 

Purification  Works,  Columbus.  Qhio   1146  213 

VIII         Scioto  River  Pumping  Station  and  Water  Purification  Works: 

Plans  Showing  Location  of  Structures   1146  221 

IX.  Scioto  River  Pumping  Station  and  Water  Purification  Works: 

General  Plan,  Showing  Arrangement  of  Structures  and  Piping. .  1146  227 

X.  Plan  of  Scioto  River  Pumping  Station   1146  829 

XT.  Scioto  River  Pumping  Station:  Section  Through  Engine-Room. 

Looking  East   114G  231 

XII.  Water  Purification  Works:  Floor  Plans  of  Main  Building   1146  283 

XIII.  Water  Purification  Works:  Substructure  of  Head-House   1146  235 

XIV.  Interior  Views  of  Filters  and  Filtered- Water  Reservoir,  Showing 

Construction,  and  Sciolo  River  Pumping  Station   1146  239 

XV.  Plan  and  Sections  of  Lime  Saturators   114<>  241 

XVI.  Plan  and  Sections  of  Mixing  Tanks   1146  243 

XVII.  Plans  and  Sections  of  O  te-House  and  Main  Dividing  Wall  of 

Settling  Basins   114(5  245 

XVIII.  Details  of  Filter  Gallery   114H  217 

XIX.  Details  of  Filters   1146  24ft 

XX.  Details  of  South  Filtered-Water  Reservoir   1146  251 

XXI.  Interior  Views  of  Filter  Gallery,  Chemical  Mixing  Room,  Lime 

Saturator  House,  and  View  of  Settling  Basins   114(i  858 

XXII.  East  Side  Sewage  Pumping  Station:  Plan  and  Section  Showing 

Machinery  .'   1144)  281 

XXIII.  General  Plan  of  Sewage  Purification  Works   114(i  888 

XXIV.  Sewage  Purification  Works:  Location  of  Structures  and  Plan  of 

Pipes  and  Conduits   114C  289 

XXV.  Plans  and  Sections  of  Septic  Tanks   114H  291 

XXVI.  Views  of  Primary  and  Secondary  Septic  Tanks   1146  293 

XXVII.  Sections  of  Gate-House   1146  295 


V  I 


PLATE                                                                                                                                                 PAPER  PACE 

XXVIII.  Plan  of  Sprinkling  Filter  No.  3   1146  2*>7 

XXIX.  Details  of  Sprinkling  Filters   1146  2W) 

XXX         Views  of  Sprinkling  Filters,  During  Construction   1146  301 

XXXI.      Plan  and  Sections  of  Settling  Basins   1146  303 

\  XXII.     Views  of  Sprinkling  Filters  Nos.  1  and  8,  and  of  Septic  Tanks   1146  305 

XXXIII.  Details  of  Pump-House   1146  307 

XXXIV.  Views  Showing  Settlement  of  Street,  Etc.,  in  Thirty-third  Street. 

in  Front  of  Cambridge  Building   1148  555 

XXXV.  Views  Showing  Cracks  in  Wall  and  Ceiling  of  Wain  Floor,  and 

Settlement  in  Area,  Cambridge  Building   1148  557 


AMEKICAN  SOCIETY  OF  CIVIL  ENGINEERS 

I  N  S  T  I  T  U  T  ED  1858 


TRANSACTIONS 

Paper  No.  1143 

NOTES  OX  THE  REPLACING  OF  THE  SUPERSTRUC 
TURE  OF  THE  HARLEM  SHIP  (  ANAL  BRIDGE.* 

By  Horace  J.  Howe,  M.  Am.  Soc.  C.  E. 

Wnii   Discussion  by  Messrs.  Lincoln  Bush,  Martin  (Ian. 
St.  John  Clarke,  Theodore  Belzner,  Frank  YY. 
Skinner,  and  Horace  J.  Howe. 


The  highway  in  upper  Manhattan  which  was  known  as  King's 
Bridge  Road  in  Washington's  time  was  the  only  connection  by  land 
from  New  York  City  to  Albany  and  Boston.  Going  north  from  Fort 
Washington,  its  location  is  easily  surmised  to-day,  winding  along  the 
base  of  the  foot-hills  to  the  present  Ship  Canal,  thence  branching  to 
the  right,  over  Farmer's  Bridge  (built  in  1759),  and  then  to  the  left 
and  over  King's  Bridge  (built  in  1693),  to  Westchester  County,  cross- 
ing the  tidal  stream  early  named  Spuyten  Duyvil  Creek. 

In  the  celebrated  retreat  to  White  Plains  (1776),  a  dozen  miles  to 
the  northeast,  these  bridges  were  useful;  and  the  British  likewise  found 
them  so,  on  their  return  from  that  battle  ground,  in  their  rapid  march 
to  capture  Fort  Washington.  These  operations  were  in  a  way  typical 
of  the  border  warfare  in  this  vicinity  during  the  ensuing  seven  years, 
or  until  the  evacuation  of  the  city  (1783),  and  no  doubt  tested  the 
bridges  severely  as  to  their  loading  and  as  arteries  of'  traffic.  King's 
Bridge  was  24  ft.  wide  and  Farmer's  Bridge  18  ft.  wide. 

Happily,  such  conditions  did  not  recur,  and  it  was  not  until  1900 
that  a  third  bridge  over  the  creek  at  Broadway  came  to  their  assistance. 

*  Presented  at  the  meeting  of  January  5th.  1910. 


2 


REPLACEMENT  OF  THE  HARLEM   SHIP  CANAL  BttlOGE 


Fk;.  L, 


REPLACEMENT  OF  THE  HARLEM   SHIP  (  ANAL  BRIIXiE 


Owing  to  the  march  of  progress,  all  three  will  be  taken  down  in  the 
near  future,  and  the  former  stream  will  be  filled  in  completely.  * 

This  is  due  primarily  to  the  excavation  by  the  United  States  Govern- 
ment of  what  is  known  as  the  Ship  Canal  (1894),  a  waterway  which 
connects  the  Harlem  and  the  Hudson,  saves  distance  to  points  on  the 
Harlem,  and  enables  1  000-ton  barges  to  cut  across  to  the  East  River 
and  avoid  the  dangers  of  the  trip  around  the  Battery.  It  required  a 
swing  bridge  with  equal  waterways  of  100  ft.  in  the  clear,  and  at  each 
end  an  approach  span  100  ft.  long  at  King's  Bridge  Road,  or  Broadway, 
as  it  is  now  called. 

The  moving  of  this  recently  built  bridge  and  the  substitution  of 
the  present  one  is  the  subject  of  this  paper. 

The  change  was  agreed  to  by  four  interested  parties,  and  resulted, 
in  short,  in  a  bridge  with:  Three  elevated  tracks  for  the  Interborough 
Rapid  Transit  Company;  two  surface  tracks  for  the  Metropolitan 
Street  Railway  Company;  an  additional  track  underneath  (four  in 
all)  for  the  New  York  Central  and  Hudson  River  Railroad;  and 
a  roadway  increased  to  35  ft.  in  width,  and  sidewalks  increased  to  7  ft. 
in  width. 

The  City  of  New  York,  furthermore,  took  over  the  old  superstruc- 
ture for  use  at  University  Heights,  a  mile  up  the  river. 

The  work  was  done  by  John  B.  McDonald  (Contract  No.  1  of 
February  21st,  1900),  under  the  direction  of  the  Board  of  Rapid  Transit 
Commissioners. 

Permission  from  the  War  Department  was  duly  obtained,  subject 
to  the  condition  of  maintaining  for  the  new  spans  at  all  times  a  clear 
waterway,  250  ft.  wide  and  15  ft.  deep,  and  a  minimum  clearance  of 
24  ft.  above  high  water  of  spring  tides. 

Permission  was  obtained  also  from  the  Bridge  Department  of  the 
City  of  New  York,  which  considered  the  neighborhood  carefully,  and 
issued  a  permit  allowing  a  "closing  of  the  said  Ship  Canal  Bridge  to 
street  travel  for  a  total  time  of  five  days  of  which  not  more  than  three 
days  shall  be  consecutive."  , 

Thus  the  preliminaries  were  arranged,  but  direct  contract  work  was 
delayed  until  1905,  which  permitted  a  study  of  the  situation  in  detail. 

The  Harlem  River  is  an  inland  stream,  about  6  miles  long,  subject 
to  tidal  influences  from  both  ends — at  the  west  via  the  Narrow?  and 
the  Hudson  River,  and  at  the  east  via  Long  Island  Sound  and  I  Ml 


I  REPLACEMENT  OF  THE   II  WM.K.M   SJ11L'  CANAL  BRIDGE 


Gate.  The  mean  rise  near  the  bridge  is  4.1  ft.,  and  the  extreme  range 
fs  perhaps  10  ft.  The  velocity  of  the  current  at  mid-tide  is  somewhat 
more  than  2  miles  an  hour;  hut  the  tide  and  velocities  are  very  variable 
and  not  to  be  anticipated.  There  is  considerable  summer  traffic  on 
the  river. 

Soundings  were  taken  at  various  points,  and  Messrs.  Terry  and 
Tench,  the  sub-contractors,  decided  to  construct  falsework  for  the  new 
draw-bridge  off  shore  at  21Gth  Street  (Manhattan),  i  mile  above  the 
site,  221st  Street,  and  to  construct  the  approach  spans  on  shore  near 
Broadway.    It  was  thought  that  dredging  would  not  be  necessary. 

Pile-driving  began  at  216th  Street,  in  May,  1905.  There  were  15 
bents  of  10  piles  each,  and  3  bents  of  15  each  at  the  center,  all  being 
spaced  carefully  with  relation  to  the  floor-beams  and  the  pivot.  Besides, 
two  clusters  were  driven,  one  at  each  outside  end,  for  protection  against 
river  craft,  and  some  others  to  connect  with  the  bank.  The  piles  were 
of  good  size,  as  long  as  55  ft.  on  the  deeper  side,  and  were  driven 
practically  to  refusal,  penetrating  from  10  to  20  ft.  into  the  river  bed,  but 
not  to  bed-rock.    The  capping  and  bracing  were  finished  in  September. 

South  Approach  Span. — Meanwhile,  the  framing,  bracing,  and  deck- 
ing of  the  bents  for  the  south  approach  span  was  completed  by  August 
1st,  and  erection  begun. 

The  total  force  at  this  time  was  50  men,  using  two  scows  (100  By 
30  ft.),  and  a  well-equipped  steam  lighter  with  a  steel  derrick.  The 
riveting  was  completed  by  October  1st,  and  the  special  work  for  the 
surface  tracks  by  October  14th.    There  were  14  000  field  rivets. 

The  general  scheme  was  to  move  the  old  span  out  and  the  new 
one  in,  simultaneously,  by  land  and  water. 

The  span,  having  been  built  with  a  panel  projecting  over  the  bulk- 
head, was  at  this  time  resting  at  that  end  on  the  cribbing  of  the  scow, 
and  at  the  other  end  on  two  sets  of  cribs  on  railroad  trucks  and  tracks. 
All  masonry  parapets  interfering  with  the  sliding  of  the  new  span 
eastward  to  place  were  removed,  anchor-bolts  were  cut,  and  steel  wedges 
inserted,  and  a  double  track  was  lined  and  surfaced  parallel  to  the 
bulkhead,  and  at  its  level. 

On  October  17th,  the  new  span,  weighing  330  tons,  was  moved 
diagonally  northwest  about  50  ft.  to  a  point  115. ft.  west  of  its  final 
position,  thereby  providing  room  for  the  two  scows  to  act  in  tandem. 
(Fig.  1,  Plate  I.)    All  end  posts  were  then  freed,  and  the  span  was  sup- 


PLATE  I. 
TRANS.  AM.  SOC.  CIV.  ENGRS. 
VOL.  LXVII,  No.  1143. 
HOWE  ON 
HARLEM  SHIP  CANAL  BRIDGE. 


Fig.  '2.— North  Span.  Harlem  Ship  Canal  Bridge,  at  Beginning  ok  Erection 


REPLACEMENT   OF   THE    II  AIM. I  . M    SHIP   CANAL   BRIDGE  0 

ported  at  intermediate  panel  points  by  a  scow  at  the  north  end  and  the 
two  sets  of  trucks  at  the  south  end. 

On  October  19th,  at  low  water  (5  a.  m.),' the  old  approach  span, 
weighing  240  tons,  having  boon  cribbed  up  on  trucks  at  one  end,  was 
wedged  up  on  the  scow  at  the  other  end.  At  8  a.  m.,  the  north  end 
rose  clear  of  the  pier.  Some  delay  ensued,  and  it  was  not  until  10.45 
a.  if.  that  the  strain  was  put  on  the  wire  ropes  from  the  drums  of  the 
stationary  engine.  Two  pulley  blocks  were  used  in  connecting  with 
the  trucks  of  the  old  span,  and  one  three-sheave  block  with  the  new. 
Both  were  adequate,  and  the  entire  mass  was  moved  out  easily,  until 
the  old  span  was  entirely  clear  of  the  masonry.  Owing  to  the  settle- 
ment of  the  tracks  by  this  move,  and  to  the  fact  that  the  tide  had 
risen,  the  4-in.  clearance  of  grillage  beams  and  abutment  was  reduced 
to  scraping  distance,  and  for  a  few  minutes  the  success  of  the  last 
half  of  the  moving  was  a  matter  of  conjecture.  However,  the  span 
was  moved  in  14  min. 

A  temporary  plank  roadway  was  begun  at  once,  and  the  first  vehicle 
passed  over  the  bridge  at  5.45  p.  m.  At  noon  the  Barber  Asphalt  Com- 
pany began  concreting  the  buckle-plate  floor,  and  completed  the  east 
roadway  on  October  25th. 

North  Approach  Span. — The  erection  of  separate  cribs  for  the  new 
112-ft.  span  was  begun  on  September  5th,  1905,  about  300  ft.  east  of 
Broadway.  (Fig.  2,  Plate  I.)  The  trusses  were  at  39-ft.  centers,  and 
there  were  five  panels,  the  same  as  in  the  south  span;  the  total  weight 
was  380  tons.  Cribs  were  erected  under  alternate  floor-beams,  leaving 
one  panel  overhanging  the  bulkhead.  The  foundation  course  was  com- 
posed of  twelve  10  by  16-in.  pieces  laid  side  by  side;  the  second  course 
was  four  16  by  16-in.  pieces,  square  with  the  first,  and  the  top  half  of 
each  crib  was  made  up  of  three  12  by  12-in.  pieces  of  diminishing 
lengths.  The  level  of  the  top  was  made  10  in.  higher  than  the  ultimate 
position  of  the  bottom  of  the  floor-beams. 

Erection  was  begun  on  September  12th,  and  took  two  weeks.  Then 
riveting  began,  and  was  finished  on  October  2Sth.  There  were  1G  000 
field  rivets,  practically  all  driven  by  power.  Meanwhile,  the  New  York 
Central  and  Hudson  "River  Railroad  Company  completed  the  new  north 
abutment. 

During  this  time,  much  care  was  taken  in  lining,  squaring,  and 
leveling  the  trusses  .and  floor-beams.    Owing  to  the  direction  of  the 


G 


i!i:rL ack.m  i:\ r  of  j  in;  ii  aulem  ajiu*  canal  biuduk 


shore  line,  it  was  impossible  to  erect  the  span  exactly  square  with  its 
final  position  at  Broadway,  and  it  was  necessary  to  roll  it  and  float 
it  20  ft.  to  the  south.  *To  do  this,  four  tracks  were  laid,  a  pair  of 
trucks  was  placed  under  each  north  post,  and  the  weight  was  deposited 
on  them.  A  scow,  as  before,  took  the  other  end,  and,  by  the  aid  of  a 
stationary  engine  with  its  lines,  the  move  was  easily  made,  and  the 
two  south  panels  extended  over  the  water.  There  was  not  room 
enough  for  another  scow,  and  so  the  weight  was  again  dropped  on  the 
original  cribs  and  the  scow  floated  off.  This  left  the  span  exposed  to 
river  craft. 

At  the  next  ebb  tide,  the  second  panel  point  was  supported  by  a 
scow.  Likewise,  the  weight  at  the  north  end  was  transferred  at  its 
second  panel  point,  and  all  was  made  ready  for  a  run  westward.  There 
were  two  tracks  on  the  shore  end.  On  November  2d  the  span  was  moved 
westward  to  near  Broadway  by  using  a  stationary  engine  and  deadman. 

The  next  step — the  track  extension  westward — was  a  puzzling 
problem,  for  the  channel  was  only  40  ft.  wide  between  pier  and  bulk- 
head, and  the  latter  curved  sharply  to  the  south,  west  of  Broadway, 
and  it  was  important  to  insure  the  different  clearances  of  the  scows. 
Finally,  a  track  of  200  ft.  radius  was  laid  out,  carefully  eased  off  at  the 
approach,  super-elevated  and  braced  against  the  neighboring  bank. 

It  was  foreseen  that  the  cribs  would  have  to  turn  on  the  trucks,  m 
a  manner  similar  to  that  of  a  car  body,  and,  to  provide  for  this,  two 
iron  bearing  plates,  well  greased,  were  set  in  place,  but  not  fastened. 
The  north  end  of  the  old  span  required  three  trucks,  one  under  each 
chord,  and  the  new  span  required  two  double  trucks,  a  pair  under  each 
point  of  support.  All  walls,  anchor-bolts,  steel  wedges,  etc.,  were 
regulated  as  before. 

On  November  6th  at  low  water  (10.30  a.  m.),  a  scow  was  floated 
under  the  south  end  of  the  old  span,  and  3  ft.  west  of  the  other  scow. 
The  clearance  of  the  northwest  corner  of  the  pier  was  8  in.,  and  of  the 
northeast  corner  18  in. 

A  stationary  engine  had  been  placed  200  ft.  west,  and  lines  had 
been  passed  to  the  trucks  of  both  spans  and  attached.  The  derrick- 
lighter  was  placed  east  of  both  spans  and  connected  with  a  deadman 
west  of  the  bridge.  It  was  calculated  that  the  lighter  would  counteract 
i In'  netion  of  the  tide  against  the  scows,  and  in  general  would  preserve 
proper  relations  with  the  trueks. 


REPLACEMENT  OF  THE   II  MM. KM    Mill'  CANAL  BRIDGE  7 


The  combined  effect  of  the  pumps  and  the  tide  caused  the  old  span 
to  rise  clear  of  the  pier  at  2.00  p.  m.  An  hour  or  so  later,  levels  showed 
the  new  span  to  he  an  average  of  10  in.  ahove  the  bridge  seat. 

At  3.25  p.  m.,  the  signal  was  given  to  move,  and  in  2  min.  the  com- 
bined mass  had  moved  70  ft.,  and  the  westerly  truck  was  at  the  west 
end  of  the  curve.  An  examination  of  the  bearing  plates  at  the  west 
trucks  of  the  old  span  showed  that  the  upper  plates  had  slid  along  the 
lower  ones  and  were  nearly  off;  also,  that  the  axles  of  the  east  trucks 
under  the  old  span,  and  of  all  the  trucks  of  the  new  span,  were  bending 
or  bowing  up  in  the  middle,  under  the  excessive  strain. 

This  condition  was  partly  caused  by  the  undue  pushing  of  the 
lighter.  A  halt  was  called,  the  cribs  were  jacked  up,  and  the  old  span 
was  moved  separately  to  a  clearance  point,  shortly  after  5.00  P.  M. 

At  5.45  p.  M.  the  new  span  was  moved  to  place,  the  lines  were  cast 
off,  and  pumps  set  to  work.   By  7.00  p.  m.  the  south  end  was  at  rest. 

The  north  end  was  landed  by  using  GO-ton  jacks,  after  a  hard 
struggle  lasting  until  midnight.  The  liquid  seemed  to  have  affected 
the  packing  and  caused  leaks,  while  the  tide  caused  much  variation  in 
the  cribbing  from  time  to  time. 

The  bridge  had  been  closed  to  vehicles  from  1.30  to  10.15  P.  m., 
and  to  foot  passengers  from  3.00  to  5.00  p.  m.  Planking  had  been  laid 
previous  to  moving. 

A  week  later,  the  old  north  approach  span  was  loaded  on  two  scows, 
and,  with  the  help  of  two  tugs,  was  floated  to  the  south  shore,  west  of 
the  bridge,  rolled  on  tracks  far  enough  to  clear  the  canal,  and  then 
cribbed  up  until  required,  a  year  later. 

The  asphalt  roadway  was  completed  on  November  17th,  1905. 

The  Neiu  Draw -Span. —The  erection  of  the  new  draw-span  began 
early  in  December,  and  continued  until  the  strike  of  January  1st,  1000. 
Union  labor  had  been  getting  $4.50  for  8  hours'  work  and  wanted  $5.00. 
The  strike  lasted  until  February  12th,  when  a  compromise  was  effected. 
Little  of  importance  occurred  meantime.  The  weather  was  particu- 
larly fine,  but  later  became  an  element  of  expense.  Some  temporary 
wood  bracing  was  put  into  the  old  approach  spans  for  protection,  and 
odd  jobs  were  attended  to.  Also,  the  New  York  Central  and  Hudson 
River  Railroad  began  running  trains  under  the  north  span. 

On  February  14th,  power-riveting  began  on  the  roadway  stringers 
and  floor-plates  of  the  motor  platforms.    The  force  was  soon  increased 


8  REPLACEMENT  OF  TIIK  HARLEM  SHIP  CANAL  BRIDGE 


to  45  men.  All  cross-girders  had  been  lined  and  leveled  some  weeks 
before,  but  required  constant  examination.  The  concentration  of  load- 
ing had  been  near  the  middle  bents,  but,  of  course,  decreased  as  the 
top  work  advanced.  Two  derrick-lighters  were  moved  about  the 
structure  on  both  sides,  and  bumped  the  piles  more  or  less;  and  the 
stationary  engine  and  riveting  guns  added  somewhat  to  the  vibrations. 

On  February  24th,  the  new  south  span  was  connected  with  (he 
viaduct  south  of  it.  The  temporary  terminal  station  at  221st  Street 
was  opened  a  month  later. 

Cracks  having  been  discovered  in  the  27  by  $-in.  connecting  angle 
plates  of  the  pivot  and  loading  girders,  new  ones  were  ordered,  and 
arrived  early  in  March.  After  much  cutting  out  of  all  rivets  affected, 
the  girders  were  riveted  up  with  1-in.  rivets  as  before.  It  was  decided 
that  the  material  was  good,  but  having  been  shipped  in  an  exposed 
manner,  attached  to  the  girder,  the  damage  had  occurred  in  transit. 

The  maximum  force  was  70  men,  including  8  riveting  gangs  of  4 
men  each.  In  this  span  122  000  field  rivets  and  7  000  bolts  were  used. 
By  the  end  of  March  the  main  trusses,  with  sway  and  lateral  bracing, 
were  erected.  The  eye-bars  had  been  easily  connected,  as  the  ends  of 
the  trusses  had  been  raised  1J  in.;  but  the  cross-strut  at  the  king-posts 
was  a  tighter  fit. 

The  adjustment  of  the  machinery  in  connection  with  the  electric 
motors  proceeded  until  the  last  of  April,  and  from  this  time  until  the 
middle  of  June,  the  draw-span  remained  on  the  falsework. 

Moving  the  Old  South  Approach  Span. — On  May  1st,  190G,  the  old 
south  approach  span,  weighing  240  tons,  was  floated  to  University 
Heights  on  two  scows,  after  having  been  run  off  the  bulkhead  on  three 
tracks.  There  was  some  delay  at  one  corner  in  detaching  it  from  the 
shore  crib.  The  contractors  ordered  fresh  jacks,  and  the  crib  timbers 
wore  cut  and  slashed  in  order  to  drop  that  end  clear  of  its  support. 
This  was  a  typical  operation. 

It  was  high  tide  when  the  destination  was  reached,  and  the  scows 
wore  straddling  the  end  draw-pior.  Rollers  were  ready  on  the  pier,  and 
there  was  no  delay  in  working  the  span  westward  to  the  temporary 
cribbing  on  the  bulkhead;  whence,  a  few  days  later,  it  was  rolled  still 
farther  west  to  the  final  position  on  three  well-braced  columns. 

Work  al  the  Old  T)rUw-Span. — The  first  thing  done  in  the  work 
at  the  old  draw-span  was  tho  chocking  of  tlio  eye-ban  of  tlio  top  chord 


Fig.  2.— Old  Draw-Span  Floating  hy  New  Span,  en  Route  to  University  Heights 


REPLACEMENT  OF  THE  HARLEM   SHIP  CANAL  BRIDGE 


9 


in  order  to  provide  for  compressive  strains  while  in  transit  to  University 
Heights.  This  was  early  in  May,  1906.  As  the  new  draw  was  to  rest 
on  a  center  pivot,  and  was  to  have  only  a  few  balance  wheels  or  "tippers" 
on  the  outside  rim,  it  was  necessary  to  dress  the  masonry  down,  and 
furnish  filler  plates  to  take  the  new  casting  (8  ft.  6  in.  in  diameter), 
and  transfer  the  weight  to  the  pier;  but,  as  the  old  rack  was  to  gear 
with  two  pinions  with  vertical  shafts,  as  before,  it  was  important  that 
the  center  of  the  rack  and  the  center  of  the  pivot  should  correspond. 

Precise  measurements  were  accordingly  taken  inside  the  old  drum 
and  resulted  in  finding  and  referencing  the  true  point.  This  was  then 
transferred  by  transit  sidewise,  up  over  the  drum  and  thence  to  the 
roadway,  where  it  became  the  governing  point  in  lining  up  the  spans. 

Late  in  May,  the  old  anchor-bolts  were  cut,  and  the  center-pin  and 
casting  were  suspended,  together  with  the  radiating  rods  and  struts. 
The  old  rack  was  left  in  place,  and  a  new  one  was  put  in  at  University 
Heights.    One  pinion  was  disconnected. 

The  old  wooden  trestle,  used  as  an  oiling  platform,  was  torn  down, 
as  it  was  designed  to  oil  the  new  shafting  while  the  draw  was  closed. 

Four  submarine  armored  cables  were  laid  across  the  channels  in  a 
trench,  up  the  center  pier,  and  through  drilled  holes  in  the  coping. 
Meantime,  electric  motors  had  been  installed  at  the  216th  Street  site, 
with  a  view  to  the  immediate  operation  of  the  bridge  on  its  arrival 
at  Broadway.  All  riveting  had  been  completed,  and  the  compressors 
had  been  removed. 

As  it  was  necessary  to  use  four  scows  to  carry  the  draw,  some  of 
the  piles  of  the  platform  had  to  be  removed.  This  left  two  bents  at 
each  end  and  five  bents  under  the  center,  supporting  the  entire  weight 
of  the  draw  and  the  platform.  The  removal  of  the  piles  was  completed 
on  May  22d.  ■  Levels,  taken  two  days  later,  showed  that  there  had  been 
no  settlement.  The  total  settlement  for  the  year,  however,  had 
been  3  in. 

On  the  new  draw  as  well  as  the  old,  the  true  center  of  the  pivot  was 
carried  up  precisely,  and  located  on  the  roadway.  Measurement  to  the 
curved  end  faces  showed  a  discrepancy  of  i  in.,  an  error  not  at  all 
serious  in  its  relation  to  the  clearances  of  the  approach  spans. 

Temporary  plank  sidewalks  and  half  of  the  roadway  were  laid. 

In  the  early  part  of  June,  as  the  days  went  by  and  the  impending 
move  was  not  made,  it  was  reported  that  the  draw  was  creeping  south 


10  REPLACEMENT  OF  THE  HARLEM   SHIP  CANAL  BRIDGE 


ward  on  its  falsework,  now  much  reduced,  as  stated.  Observation 
showed  that  some  of  the  piles  were  out  of  plumb,  and  that  the  caps 
were  sagging  on  the  center  bents.  Fixed  lines  by  instrument  were 
established  on  shore,  and  sights  were  taken  at  regular  intervals  for  the 
next  week  or  more;  but  only  temperature  variations  were  to  be  seen. 
The  average  load  on  each  pile  was  12  tons. 

There  was  no  disposition  to  delay  the  work,  it  may  be  imagined, 
particularly  as  the  center  pier  at  University  Heights  was  completed; 
and  operations  were  prosecuted  with  great  energy  by  Superintendent 
J.  F.  Sullivan  and  his  force  of  50  men,  up  to  June  14th,  when  the  old 
draw  was  moved  up  the  river  to  its  present  location.  On  that  day  at 
low  water  (10.15  a.  m.)  it  was  swung  for  the  last  time  at  Broadway 
through  an  angle  of  35°,  lining  up  northeast  and  southwest,  and  just 
clearing  the  approaches.  Two  scows  with  well-braced  cribbing  were 
floated  under  each  arm  and  placed  parallel  to  the  channel,  after  allow- 
ing for  the  proper  clearances  at  207th  Street.  The  suspended  drum, 
etc.,  was  braced  and  guyed  to  the  adjoining  scows.  The  weight  was  900 
tons,  exclusive  of  cribbing,  and  the  displacement  of  each  scow  was 
rated  at  500  tons.    (Fig.  1,  Plate  11.) 

The  scows  had  4  ft.  of  water  inside,  and  after  the  wedging  and 
blocking  up  had  been  done,  pumping  was  commenced  by  the  aid  of 
steam  from  four  tugs,  two  lighters,  and  a  boiler-scow.  There  were 
three  2-in.  streams  from  the  north  and  south  scows,  and  two  streams 
and  an  8-in.  centrifugal,  from  the  other  scows. 

12.30  p.  If. — The  rim  wheels  were  barely  off  the  circular  tread,  and 
the  tide  had  risen  nearly  2  ft.,  as  noted  on  the  neighboring  tide  gauge 
of  the  Dock  Department. 

1.45  P.  M. — The  scows  wore  3  ft.  out  of  water,  and  the  depth  of  water 
in  the  hold  was  1|  ft. 

2.15  p.  M. — The  lower  struts  or  arms  to  the  rack  (which  had  been 
sawed  off)  were  clear,  except  at  the  west  side,  where  much  wedging  and 
jacking  was  being  done. 

2.35  p.  M. — All  clear;  the  bridge  drifted  eastward,  grazing  first  one 
approach  and  then  the  other. 

2.45  p.  m. — The  lower  struts  cleared  the  southeast  corner  of  the 
circular  rack,  and  the  tugs  signaled  "Go  ahead."  The  bridgemen, 
being  no  longer  needed  at  jacks,  lines,  etc.,  were  relieved  temporarily. 
Two  tugs  (each  rated  at  400  h.p.)  were  placed  in  front  and  two  in  the 
rear,  and  they  were  shifted  about  in  going  around  the  bend  and 
approaching  their  destination.    Full  control  was  maintained  through 


Fig.  2.— The  Present  Haklem  Ship  Canal  Bridge 


REPLACEMENT  OF  THE  HARLEM  SHIP  CANAL  BRIDGE 


1  1 


out  the  passage,  the  only  incident  being  the  considerable  amount  of 
mud  stirred  up  at  one  point  by  one  of  the  tugs.  The  writer  was 
stationed  on  one  of  the  middle  scows.  There  was  no  creaking  of  the 
top  chords,  or  other  indication  of  strain  in  the  main  trusses.  Some  of 
the  braces  about  the  drum  looked  well  "tuned-up,"  while  the  diagonals 
were  taut.   The  cribs  were  solid  and  well  connected.    (Fig.  2,  Plate  II.) 

3.45  p,  m. — Arriving  at  University  Heights,  the  various  clearances 
were  found  to  be  sufficient.  No  bumping  against  the  timber  protection 
pier  occurred.  The  diagonals  to  the  drum  slid  past  the  round  coping, 
and  the  rim  wheels  were  well  up  over  the  rack,  and,  in  fact,  afterward, 
they  raised  somewhat.  The  pumps  were  again  applied,  and  the  tide 
soon  helped  to  drop  the  mass  on  the  pier.  As  the  pivot  casting  drew 
near  to  place,  the  holes  were  seen  to  match,  and  the  anchor-bolts  were 
dropped  in. 

10.30  p.  m. — The  pinion  engaged  the  rack,  and,  steam  having  been 
maintained  all  the  way  up  from  Broadway,  the  span  was  turned  one- 
quarter  around,  and  left  in  the  open  position  above  the  pier  protection. 

Moving  the  New  Draw-Bridge. — On  the  following  morning  (June 
15th),  the  scows  were  taken  to  216th  Street  and  placed  diagonally  as 
before.  The  day  was  spent  in  adjusting  the  cribbing,  calculating  on 
the  tides,  as  usual. 

A  finder-ring  for  the  new  pivot  casting  was  placed  accurately  on  the 
old  pier,  and  wedge  plates  to  relieve  the  pivot,  were  provided  on  its 
east  and  west  sides.  At  the  end  piers,  the  latch  girders  and  wedge  plates 
were  centered  and  trued  up  generally. 

During  the  night  rain  began  to  fall  and  continued  throughout  June 
16th,  with  the  wind  in  the  east.  This  had  the  effect  of  raising  the  low- 
water  level  1.3  ft.,  and  caused  much  delay  in  cribbing  up.  Later,  the 
north  scow  grounded,  in  spite  of  this,  showing  the  need  of  dredging, 
and  causing  further  delay;  so  that,  with  high  tide  due  by  almanac  at 
6.40  P.  m.,  it  was  1.00  P.  M.  before  pumping  out  began. 

The  plant  was  the  same  as  before,  with  an  added  centrifugal  pump 
and  a  number  of  hand-pumps.  All  were  needed,  for  it  was  not  until 
4.15  P.  If.  that  the  pivot  was  clear,  although  the  ends  had  been  so  for 
half  an  hour. 

5.20  p.  m. — The  pivot  was  10  in.  clear  of  its  seat,  the  latter  being 
at  Elevation  10.94  above  mean  high  water.    The  top  of  the  pier  at  * 
Broadway  was  nearly  the  same  (Elevation  10.89)  ;  but  the  wheel  tread 
was  about  1  ft.  higher  (Elevation  12.11),  and  this  governed  the  lift  at 
216th  Street,  and  the  consequent  time  of  Btarting.  (Fig.  1,  Plate  III.) 


I? 


REPLACEMENT  OF  THE  HARLEM  BHIP  CANAL  BRIDGE 


5.55  i\  M. — The  pivot  was  14  in.  up,  and  there  was  not  much  more 
time,  as  the  tide  seemed  to  have  turned.  Tidal  records  showed  that  the 
flood  tide  was  0.4  ft.  higher  than  usual.  The  order  was  finally  given, 
and  the  immense  structure  (weighing  with  cribbing  nearly  2  000  tons) 
was  slowly  pulled  out  into  the  stream,  pivoting  on  the  northwest  corner 
and  lining  up,  broadside  to  the  north.  The  channel  was  none  too  wide, 
and  there  was  some  sweeping  away  of  blocking  into  the  river.  One  of 
the  four  tugs  was  detailed  to  butt  out  that  corner,  and  thenceforth 
there  was  no  stop  or  hindrance  until  near  Broadway,  where  speed  was 
reduced,  lines  were  cast  off,  and  the  whole  mass,  grazing  the  approaches, 
was  eased  into  its  berth.  The  pivot  casting  slid  over  the  rack  with  a 
margin  of  an  inch  or  two. 

G.35  p.  m. — The  casting,  somewhat  out  of  level,  hung  over  the  pier 
15  in.  clear,  and  there  was  ample  clearance  at  the  approaches.  Lines 
were  made  fast,  and  the  tugs  were  used,  as  before,  to  furnish  steam 
for  pumping  water  into  the  scows.  The  two  scows  at  the  north  end 
were  loaded  heavily,  the  water  being  within  18  in.  of  the  deck. 

7.00  p.  M. — Electric  connections  had  been  made,  and  lights  were 
turned  on  below  and  above. 

7.45  p.  m. — The  north  pinion  engaged  the  rack,  and,  later,  closed 
the  draw.    The  south  pinion  was  evidently  about  right. 

8.15  p.  M. — Owing  to  the  failure  of  a  centrifugal  pump,  one  of  the 
northerly  scows  had  to  be  sunk,  and  the  pivot  casting  was  4  in.  above 
the  pier  on  the  north  side,  and  6  in.  on  the  south  side,  an  inequality 
which  was  magnified  greatly  at  the  ends  of  the  draw. 

9.30  p.  m. — The  span  rested  on  the  center  pier. 

June  17th,  190G,  Sunday: 

12.30  a.  M. — The  scows  had  dropped  down,  and  were  free  from  (lie 
south  arm.    An  hour  later,  the  same  was  true  for  the  north  arm. 

3.45  a.  m. — The  bridge  was  swung  by  hand-levers,  and  the  end 
wedges  were  in  place,  but  not  adjusted. 

5.20  a.  M. — The  span  was  swung  half  around  by  electric  power,  and 
it  was  found  that  it  could  be  operated  quickly  and  satisfactorily.  The 
temporary  wooden  aprons  were  repaired,  and  the  roadway  was  opened. 

9.30  a.  m. — Measurements  at  G8°  Fahr.  showed  that  the  space  between 
the  draw  and  the  approach  span  on  the  north  side  measured  25  in.  and 
on  the  south  side  2J  in. 

The  next  week  was  spent  in  shipping  away  timber,  thereby  releasing 
the  scows,  removing  the  chocks  from  the  top  chords,  taking  down  the 
pile  platform,  adjusting  the  aprons,  wedges,  and  pinions,  installing  the 
•  two  circular  feeder  tracks  at  the  pivot,  and  connecting  with  the  third 
rails  above.  By  the  end  of  June,  the  approach  S{rtnis  had  been  lined  up, 
and  the  rocker  posts  plumbed  up.  The  asphalting  was  also  well 
advanced. 


Ulil'LACKMKNT  OF  TIIK   IIAIM.K.M    SHIP  CANAL  BRIDGE 


It  was  decided  to  put  in  fixed  aprons  on  the  approach  spans,  and  to 
close  the  span  in  one  position  only  (without  reversing),  on  account  of 
the  number  of  important  rail  connections.  Later,  it  was  found  neces- 
sary to  stiffen  the  rack  with  iron  knees,  at  intervals. 

Much  of  the  new  equipment  was  done  by  the  Bridge  Department  of 
New  York  City,  in  accordance  with  its  practice  on  the  Harlem. 

This  is  the  only  pivot-bearing  draw  on  the  river.  The  weight  on  the 
pivot  is  1  500  tons.  It  is  operated  by  two  60-h.p.  electric  motors,  and. 
considering  its  weight,  is  handled  more  easily  and  quickly  than  any 
other.  Occasionally,  it  delays  traffic,  while  opening  and  closing,  for  a 
period  of  only  4  min.  In  addition  to  signals  by  whistle,  and  electric 
bells,  there  is  a  telephone  connection  (seldom  used)  between  tower  and 
engine-room.    (Fig.  2,  Plate  III.) 

During  1907  and  1908,  the  shafting  was  partially  renewed  several 
times,  due  to  causes  which  were  exceedingly  difficult  to  locate,  but 
resulting  in  twisting  the  shafting.  In  June,  1907,  the  latch  girders 
were  firmly  fixed  by  reinforced  concrete  around  and  about  them  for  the 
entire  distance  between  the  pedestals,  and  thus  the  play  at  the  ends  of 
the  draw  was  much  reduced. 

The  contract  price  for  removing  the  old  bridge  and  replacing  it 
with  the  new  one  was  about  $250  000. 

Old  North  Approach  Span. — In  November,  1907,  the  old  north 
approach  span,  which  had  been  left  on  the  south  bank,  was  rolled  toward 
the  river  and  received  by  scows,  in  much  the  same  manner  as  described 
previously.  The  scows  floated  broadside  through  the  draw  channel, 
and  were  afterward  swung  around,  with  one  tug  in  front  and  one  in 
rear.  The  top  of  the  east  pier  at  University  Heights  was  over-run 
comfortably,  and  the  rollers  did  the  rest.  As  no  water  was  pumped  into 
the  scows,  several  tides  were  necessary  before  the  final  position  on  the 
masonry  was  reached  (November  29th,  1907). 

University  Heights  Bridge  was  declared  open  by  Mayor  George  B. 
McClellan  on  January  8th,  1908. 

In  all  these  operations,  extending  over  a  period  of  two  years,  there 
was  no  accident  of  a  serious  character  to  any  of  the  force  employed. 

The  Rapid  Transit  Commissioners  were  represented  by  George  S.« 
Rice,  M.  Am.  Soc.  C.  E.,  Chief  Engineer.  Alfred  Craven,  M.  Am.  Soc. 
C.  E.,  Deputy  Chief  Engineer,  Sverre  Dahm,  M.  Am.  Soc.  C.  E.,  Gen- 
eral Inspector  of  Designs,  and  by  C.  V.  V.  Powers,  M.  Am.  Soc.  C.  E., 


1 1 


REPLACEMENT  OF  THE  IIAKLKM   SHIP  CANAL  BKIIXiE 


Division  Engineer.  The  writer  acted  as  Resident  Engineer,  and  takes 
this  occasion  to  make  grateful  mention  of  his  subordinates,  who  con- 
tinuously gave  their  best  services.  They  were,  from  time  to  time,  as 
follows : 

Messrs.  R.  A.  Berry,  L.  C.  Devery,  J.  D.  P.  Hogue,  R.  J.  Smyth, 
0.  M.  Torpey,  and  W.  P.  Vallely,  Assistant  Engineers;  W.  C.  Martin, 
Rodman,  and  Theodore  Belzner,  Jun.  Am.  Soc.  C.  E.,  Inspector. 

The  Rapid  Transit  Construction  Company  was  represented  by 
George  H.  Pegram,  M.  Am.  Soc.  C.  E.,  Chief  Engineer,  and  A.  S.  F. 
Berquist,  M.  Am.  Soc.  C.  E.,  Inspector  of  Steel. 

Historical  Notes. 

In  searching  for  records  of  similar  operations,  the  first,  chronologi- 
cally, of  any  magnitude,  is  seen  to  be  the  first  in  magnitude  with 
reference  to  the  tonnage  moved,  if  not  in  regard  to  the  velocity  of  the 
current  and  the  exposure  to  gales;  and,  later,  in  relation  to  special 
appliances  used  in  raising  to  place.  This  was  the  work  of  Robert 
Stephenson  in  connection  with  the  Conway  and  Britannia  Bridges,  as 
recorded  chiefly  by  his  assistant,  Mr.  Edwin  Clark.* 

Mr.  Stephenson  had  led  up  to  those  pioneer  monuments  by  various 
achievements  in  his  practice.  He  had  acquired  habits  of  close  technical 
experimentation,  and  of  co-operation  with  other  engineers,  architects, 
parliamentary  committees,  boards  of  directors,  and,  in  fact,  with  men 
of  all  classes.  He  could  say  the  right  word  at  a  dinner;  as  for  instance 
when  he  noted  the  reduction  of  time  between  London  and  Dublin  made 
possible  by  the  bridges,  and  spoke  of  engineers  as  being  instrumental  in 
bringing  about  a  better  understanding  between  the  English  and  the 
Irish. 

It  required  a  very  able  man  to  make  the  jump  to  the  first  long- 
span  wrought-iron  bridge;  for,  as  Mr.  Clark  says,  the  process  of  uniting 
wrought-iron  plates  by  rivets  had  been  hitherto  a  peculiar  feature  of 
boiler-Work  or  iron  ship-building  and  had  been  little  resorted  to  by 
the  Civil  Engineer,  until  Mr.  Stephenson  proposed  the  construction  of 
these  bridges. 

All  wonderful  things  cease  to  become  so,  however,  when  the  separate 
steps  are  studied;  and  perhaps  the  transition  from  an  iron  ship,  with 

•  **  The  Conway  and  Britannia  Tubular  Bridp^."  London,  isr>0,  i>\  Edwin  Clark.  Re*.i 
deal  Engineer. 


REPLACEMENT  OF  THE  HAUL  EM  SHU'  CANAL  BRIDGE 


15 


ribs  and  knees  at  short  distances,  to  the  rectangular  tube,  with  web 
stiffeners  and  gussets  every  2  ft.,  together  with  the  cellular  top  and 
bottom,  borrowed  from  a  previous  design  of  his,  was  not  intrinsically 
so  great  an  innovation,  after  all. 

The  spectacle  of  an  accident  to  an  iron  vessel  and  the  evidence  of  its 
stanchncss  in  resisting  the  waves,  and  holding  together,  is  said  to  have 
exerted  a  strong  influence  on  Mr.  Fairbairn,  the  manufacturer,  and 
through  him,  on  Mr.  Stephenson,  as  to  the  ability  of  a  similar  iron 
framework  to  carry  rolling  loads. 

Later,  when  the  method  of  floating  the  tubes  was  considered,  there 
naturally  followed  the  idea  of  doing  without  the  use  of  scows,  but,  for 
good  reasons,  that  method  was  not  adopted. 

The  Conway  Bridge. — Work  was  wisely  begun  on  the  smaller  bridge, 
at  the  Conway  River  (May,  1846),  and,  after  two  years  of  experiment 
and  construction,  the  first  tube  was  floated  from  its  falsework,  some 
GOO  ft.,  to  the  site  it  now  occupies. 

Steam  riveting  machines  had  been  used  throughout,  and  half-round 
"rimmers."  The  type  of  tube  had  been  decided  chiefly  from  tests  on  a 
model  of  one-sixth  the  size  of  the  bridge.  Not  satisfied  with  this,  Mr. 
Stephenson  supported  the  tube  at  its  ends,  cut  out  the  falsework,  and 
loaded  it  with  cars  containing  iron  plates.  The  resulting  deflection 
was  so  small  that  no  similar  test  was  necessary  again. 

The  floating  of  the  tube  (26  ft.  high,  14  ft.  wide,  inside,  412  ft. 
long,  and  having  a  weight  of  1  417  tons  of  2  000  lb.)  was  done  by  six 
scows  (each  98  ft.  long,  25  ft.  wide,  and  8  ft.  deep)  arranged  in  two 
sets  of  three.  This  provided  for  an  overhang  at  each  end,  sufficient  to 
take  the  timber  seats  prepared  in  the  recesses  of  the  abutments,  at  some 
distance  from  the  shore  line.   The  tubes  were  6  ft.  6  in.  above  the  water. 

There  were  two  guide-chains  under  water,  with  which  it  was  sup- 
posed that  the  movement  could  be  controlled  in  a  manner  similar  to 
that  of  a  ferry  on  a  suspended  cable,  but  they  proved  almost  useless, 
and  most  of  the  hauling  was  done  by  two  Manila  hemp  cables,  each 
operated  from  a  50-man  capstan.  The  force  was  about  350  men,  on 
land  and  water.  A  steamer  was  at  command,  but  seems  to  have  acted 
only  as  a  utility  boat. 

Some  progress  was  made  against  the  rising  tide,  but  more  when 
it  slackened  at  the  flood,  and  enabled  the  tube  to  be  easily  hauled  to 
place,  clearing  the  abutments  by  4  in.  at  each  end.    The  average  rise 


16 


REPLACEMENT  OF  THE  HARLEM   SHIP  (  ANAL  BRIDGE 


of  the  tide  was  18  ft.  and  the  elearance  of  the  bridge  was  also  18  ft., 
so  that  a  lift  of  about  12  ft.  remained  to  be  made. 

This  was  done  by  a  hydraulic  press  (18-in.  ram  with  a  6-ft.  stroke) 
at  each  end. 

The  weight  of  the  tube  was  transferred  first  to  a  cast-iron  frame 
inside;  thence  to  eye-bars  with  pin  connections;  and  thence  to  the 
cross-head  of  the  press  above.  A  small  steam  engine  and  pump,  to 
force  water  into  the  press,  were  attached. 

Barring  the  pulling  out  of  a  cylinder  head,  and  the  delay  in  re- 
placing it  with  a  stronger  one,  the  work  was  continuous;  but  cast  iron 
was  either  eliminated  or  heavily  reinforced  with  wrought  iron  at  the 
Britannia  Bridge. 

Mr.  Stephenson  passed  through  on  the  first  locomotive  in  April, 
1848. 

It  may  be  well  to  note  here  the  early  decision  with  regard  to 
painting  plates  before  riveting  them  together,  which  was,  that  close 
contact  is  thereby  prevented.  The  claim  was  made  that  old  pieces  of 
riveted  work  were  most  sound  at  the  joints.  Where  necessary,  a  mix- 
ture of  red  and  white  lead  was  used  as  a  filler. 

The  cellular  floor  and  top  chord,  built  up  of  plates  and  angles,  wen1 
large  enough  to  allow  a  man  to  paint  them  from  the  inside.  The 
track  floor  was  cheaply  water-proofed  with  a  mixture  of  coal-tai,  lime, 
and  turpentine.  A  corrugated,  galvanized-iron  roof  was  constructed 
over  the  whole  tube. 

The  price  per  (long)  ton  was  £37,  and  the  total  cost  of  the  Conway 
Bridge  was  £145  200. 

The  Britannia  Bridge. — The  Britannia  Bridge  connects  Wales  and 
the  Island  of  Anglesey,  across  Menai  Straits.  The  two  main  spans 
are  each  460  ft.  in  the  clear,  and  were  floated  to  place,  whereas  the 
approach  spans  were  constructed  on  falsework  at  the  site. 

The  Government  required  105  ft.  clearance  above  high  water,  and 
therefore  a  hollow,  center  tower,  220  ft.  high  or  more,  was  required 
on  Britannia  Bock.  The  foundations  were  begun  on  Good  Friday, 
1846,  and  the  last  stone  was  laid  in  June,  1840,  the  masons  working 
12  hours  a  day  for  6  days  in  the  week,  in  order  not  to  hold  back  the 
tubes.  The  latter  were  30  ft.  high,  14  ft.  wide,  inside,  and  weighed 
2  150  tons. 

Tn  floating  each  tube  650  men  were  employed,  about  400  being 


REPLACEMENT  OF  CHE  ll.UM.I  M   SHIP  OAK  AX  BRIDGE 


17 


sailors  hired  for  the  occasion.  Eight  scows  were  used,  in  much  the 
same  way  as  at  the  Conway  Bridge,  and  were  guided  by  Manila  cables 
buoyed  up  by  casks.  Tarred  Manila  ropes  were  used  for  hauling, 
with  ''cable-stoppers"  and  "messengers." 

The  four  tubes  were  handled  in  conformity  with  written  instruc- 
tions, after  Mr.  Stephenson  had  made  experiments  with  models  on  a 
small  pond.  The  various  rocks  and  shoals  were  indicated,  together 
with  the  scows,  tubes,  and  lines,  and  everything  that  it  was  possible 
to  foresee  was  discussed. 

At  the  moving,  he  and  others  (including  Captain  Claxton,  who 
had  immediate  charge)  occupied  a  position  on  the  top  of  the  tube, 
and  from  that  elevation  signals  by  flags  were  given  to  each  boat 
concerned. 

Although,  in  floating  the  four  tubes,  there  were  instances  of  heavy 
cables  snapping,  and  of  severe  bumps,  yet,  in  general,  the  men  were 
equal  to  the  emergencies,  and  landed  the  tube  each  time  in  the  re- 
cesses of  the  masonry,  before  the  tide  fell.  Two  steamers  were  in 
attendance. 

The  lifting  machinery  was  considerably  improved,  the  press  having 
a  20-in.  ram,  lined  with  brass,  and  having  a  6-ft.  stroke  as  before. 
Leaks  were  stopped  with  oatmeal  gruel  and  sal-ammoniac,  and,  later, 
by  a  second  U-shaped  leather  collar  below  the  first. 

Brickwork  in  cement  followed  closely,  but,  in  spite  of  this,  the 
first  tube,  during  one  lift,  dropped  8  or  9  in.,  doing  considerable  damage. 

In  the  raising  of  each  tube,  6  ft.  per  day  was  accomplished  for  about 
16  days,  and  a  single  track  was  put  in  use  in  March,  1850.  The  fourth 
tube  was  floated  in  July,  1850. 

The  Britannia  Bridge  was  riveted  by  hand.  The  total  cost  was 
£601  S65,  and  of  this,  one-fourth  was  for  masonry.  Both  the  Conway 
and  Britannia  Bridges  are  still  in  use. 

Associated  with  Mr.  Stephenson  were  Mr.  I.  K.  Brunei,  and  Captain 
Claxton;  and  as  these  gentlemen  were  soon  afterward  engaged  at  the 
Chepstow  and  Saltash  Bridges,  in  similar  movements,  brief  mention 
of  these  may  naturally  be  made  next. 

The  Chepstow  Bridge. — The  chief  feature  at  the  Chepstow  Bridge 
Cover  the  River  Wye),  barring  the  pneumatic  process  used  in  sinking 
the  cylindrical  foundations,  was  the  design  and  erection  of  the  300-ft. 
channel  span. 


IS 


REPLACEMENT  OF  THE  HARLEM   SHIP  CANAL  BRIDGE 


The  top  chord  was  composed  of  one  wrought-iron  tube,  9  ft.  in  diam- 
eter, treated  like  a  trussed  beam  of  three  panels,  except  that  there 
were  two  suspended  chains,  with  the  track  between.  The  height  of  the 
truss  was  50  ft.  Pins  7  in.  in  diameter  were  used  at  the  ends.  A 
second  tube  for  the  other  track  enabled  lateral  bracing  to  be  introduced, 
and  stiffened  each. 

Following  out  the  cautious  method  of  the  Conway  Bridge,  the 
first  span  was  erected  on  falsework  and  tested  with  a  live  load  of  2£ 
(long)  tons  per  linear  foot.  The  wrought  iron  in  each  truss  weighed 
4 GO  (long)  tons.  It  was  then  taken  apart,  and  the  tube  itself,  sup- 
ported by  posts  and  chains,  was  floated  (April,  1852),  on  six  wrought- 
iron  barges.  It  had  to  be  done  quickly,  as  the  rise  of  spring  tides  was 
40  ft.  The  use  of  crabs  with  two  barrels  enabled  hauling-chains  to 
be  wound  without  difficulty. 

The  tube  was  lifted  by  jacks,  during  the  day,  some  40  ft.,  and, 
later,  it  was  raised  50  ft.  more,  to  its  final  position. 

A  single  line  was  opened  up  in  July,  1852.  This  was  the  first 
circular  tube  of  large  size  introduced  as  a  bridge  member. 

The  Saltash  Bridge. — In  the  Saltash  Bridge,  a  single-track  struc- 
ture across  the  Tamar  River,  nea;-  Plymouth  (also  on  the  Cornwall 
Kail  way),  the  top  chord  tube  was  made  elliptical  (16  ft.  9  in.  wide 
and  12  ft.  3  in.  high).  The  bottom  chord  was  double.  The  typo  of 
truss  was  a  bowstring,  with  the  string  curved  equally  with  the  bow. 

Mr.  Brunei*  (3d)  states  that  "the  mode  of  floating  and  lifting  the 
superstructure  had  great  influence  in  the  preparation  of  the  design" 
— meaning  cylindrical  foundations  and  cast-iron  columns,  as  well  a« 
truss  design. 

There  were  two  single  spans  of  455  ft.,  56  ft.  high,  and  each  con- 
tained 1  200  tons  of  wrought  iron.  The  bottom  chord  was  of  7  by  1-in. 
bars,  20  ft.  long.    There  was  a  solid  ballast  floor  throughout. 

The  work  was  begun  in  1853,  but  was  delayed,  on  account  of  the 
difficulty  of  founding  a  35-ft.  cylinder,  by  using  compressed  air,  af  a 
depth  of  88  ft.  below  high  water.  This  was  the  first  successful  attempt 
on  a  large  scale. 

Meanwhile,  the  superstructure  was  manufactured,  put  together,  and 
afterward  tested  at  its  falsework  by  a  live  load  of  1  340  tons,  uniformly 
distributed.    The  deflection  was  5  or  f>  in.,  and  was  deemed  satisfactory. 

*"T>>e  Lifp  of  [nambard  Kingdom  Brunei,  Civil  Engineer,"  by  [mnbsrd  Brunei. 

B.  C.  (j.,  London,  wo. 


REPLACEMENT  01'  'I'll  10   IFAHLKAI    SHIP  CANAL  BRIDGE 


I!) 


It  was  as  late  as  September  1st,  1857,  before  the  first  span  was 
moved,  and  information  in  relation  to  it  is  comparatively  meager. 
The  methods  used  at  the  Britannia  Bridge  were  followed.  The  actions 
of  the  500  men  engaged  were  regulated  in  accordance  with  printed 
instructions  which  had  been  issued,  and  with  flag  signals  from  the 
''bridge,"  where  Mr.  Brunei  and  others  were  stationed  during  the 
passage.    Mr.  Stephenson  was  too  ill  to  be  there. 

The  move  was  at  first  outward  from  the  shore,  then,  after  an  inter- 
val in  which  the  hawsers  were  shifted,  up  the  river,  endwise  to.  the 
center  pier,  then  a  quarter  turn  was  made,  and  finally,  an  accurate 
placing  by  strong  lines  at  the  piers.  There  was  a  clearance  of  a  few 
feet  above  the  water.  The  tide  was  not  swift  and  there  v/ere  no  mis- 
haps mentioned. 

The  lifting  was  done  3  ft.  at  a  time,  separately  at  each  end.  At 
the  center  pier,  cast-iron  columns  (braced)  were  built  up  as  fast  as 
these  lifts  were  made;  but,  at  the  shore  end,  the  masonry  proceeded 
more  slowly.  There  was  no  cause  for  hurry,  as  the  river  traffic  went 
through  the  other  opening.  There  was  finally  a  clear  distance  of  100 
ft.  above  spring  tides;  and  the  total  height  above  the  foundations  was 
260  ft.  to  the  highest  point  of  the  trusses. 

Three  hydraulic  presses  or  jacks  were  used  under  each  end.  The 
rams  had  a  screw-thread,  arranged  with  a  nut  in  such  a  way  that  the 
tube  was  supported  at  all  times.  Timber  packing  was  also  used.  By 
July,  1858,  the  full  height  was  reached.  The  second  span  was  floated 
successfully  soon  after.  In  May,  1859,  the  bridge  was  declared  open 
by  Prince  Albert,  after  whom  it  was  named  the  Royal  Albert  Bridge. 
The  total  cost  was  £225  000.  The  fiftieth  anniversary  has  recently 
been  celebrated,  the  old  bridge  remaining  as  it  was  originally. 

Oilier  Bridges. — Passing  by  well-known  examples  of  this  method  of 
erection — the  Moerdyck  Bridge  (1875),  the  new  Tay  Bridge  (1885), 
the  Hawkesbury  Bridge  (1889),  and  others  of  500  tons  or  less,  in 
which  about  the  same  or  similar  principles  were  involved — we  come 
(1S90)  to  the  523-ft.,  single-track,  through  bridge  across  the  main 
channel  of  the  Ohio  River,  below  Pittsburg,  on  the  Ohio  Connecting 
Railway  (Pittsburg,  Cincinnati,  Chicago,  and  St.  Louis  Railway), 
erected  by  the  Keystone  Bridge  Company,  C.  L.  Strobel,  M.  Am.  Soc. 
C.  E.,  Chief  Engineer. 

The  Government,  having  required  the  long  span  and  also  a  clear 


20 


REPLACEMENT  OF  THE  HABLEJM   SHIP  CANAL  BRIDGE 


height  of  75  ft.  above  mean  water  level,  and  having  limited  the  time 
during  which  the  river  might  be  obstructed,  it  became  necessary  to 
build  the  falsework  at  a  corresponding  height,  assemble  and  erect  the 
bridge  upon  it,  and  then  float  the  structure  to  its  site,  as  quickly  as 
possible. 

Nineteen  bents  of  5  piles  each  were  driven  and  cut  off  16  ft. 
above  the  water.  On  these  were  framed  bents  of  5  posts  each,  with  an 
80-ft.  sill  and  a  32-ft.  cap,  all  with  the  usual  railroad  trestle  dimen- 
sions. At  the  base,  across  each  alternate  bay,  20-in.  I-beams  were 
added.  Under  these  were  duly  placed  nine  ordinary  coal  barges  (130 
by  26  by  8  ft.). 

The  weight  of  the  bridge  was  about  900  tons.  The  trusses  were 
65  ft.  high.  The  bracing  of  the  bents  into  towers  and  the  binding 
of  them  together  by  rods  with  turnbuckles  was  susceptible  of  careful 
study,  and,  once  accomplished,  eliminated  the  principal  cause  of  un- 
certainty. At  Hawkesbury,  the  Union  Bridge  Company  had  effected 
this  by  a  single  pontoon,  335  ft.  long,  well  braced  with  timber  and 
wire  cables  internally,  but  with  the  superstructure  at  a  much  lower 
level.    In  both  cases,  the  hauling  to  place  was  done  by  cables. 

At  Pittsburg,  two  scows  were  fastened  to  the  bows  of  the  end 
barges  (leaving  the  three  barges  in  the  middle  unattached),  and  on 
these  scows  four  engines  controlled  the  lines  up  to  the  bridge  piers. 
The  nine  barges  were  braced  together  at  the  bow,  and.  after  floating 
out  to  clear  the  piles,  they  were  braced  likewise  at  the  stern.  The 
current  in  the  river  was  slight,  and,  although  a  couple  of  heavy  showers 
occurred  while  the  scows  were  being  moved  the  few  hundred  foot  neces- 
sary, there  was  no  bumping  against  shore  or  against  obstructions. 

The  itinerary  of  the  work  was  as  follows:* 

8.50  a.  if aj  August  10th. — Sufficient  water  had  been  pumped  from 
the  barges  so  that  the  mass  rested  on  them. 

11.15  a.  m. — The  barges  had  been  floated  out  toward  the  center  of 
the  river,  thereby  clearing  the  bents  of  piles. 

7.30  p.  m. — Water  was  again  admitted  to  the  barges,  and  the  span 
cleared  the  bridge  seats  by  2  ft. 

8.20  p.  m. — The  span  was  about  0  in.  clear.  The  work  was  blocked 
up  and  left  until  the  following  morning. 

7.30  \.  m . ,  August  20th. — The  lowering  was  continued,  so  that  the 
bridge  rested  on  its  piers.    The  barges  were  removed  later  in  the  day. 


;  KiKjiticvrituj  \(  us,  SepttMiihtM- 'JOth.  l's(-'<». 


REPLACEMENT  OF  TJIE   HARLEM    SHIP  CANAL  PR  I  DOE  21 


There  had  been  no  distortion  of  bents  or  barges,  nor  any  important 
casualty  of  any  kind. 

In  Canada,  the  Dominion  Bridge  Company  has  erected  several 
bridges  of  note,  in  this  manner. 

The  Coteau  Bridge  (1890),  across  the  St.  Lawrence  (Grand  Trunk 
Railway)  west  of  Montreal,  has  single-track  spans  of  175  to  223  ft. 

The  Shubenacadie  Bridge,  in  Nova  Scotia  (1901),  across  an  arm 
of  the  Bay  of  Fundy  (Grand  Trunk  Railway),  has  single-track  spans 
of  215  ft.,  each  weighing  150  tons. 

The  Miramichi  River  Bridge,  Newcastle,  N.  B.  (1902),  has  single- 
track  spans  of  204  ft.,  each  weighing  320  tons. 

The  French  River  Bridge,  Ontario,  a  single-track  span  of  415  ft. 
weighing  1 424  tons,  was  erected  by  the  Canadian  Pacific  Railroad 
in  1907.  This  was  slid  endwise  from  the  embankment  upon  a  scow 
(155  by  33  by  12  ft.)  and  thence  was  hauled  to  place  by  lines  from  an 
engine  on  the  scow. 

Local  difficulties  in  all  these  cases  were  overcome  successfully. 

Sand  Jacks. — The  use  of  sand  in  jacking  up  or  in  letting  down 
bridges  of  moderate  tonnage  dates  back  to  1S78,  or  even  earlier,  in 
Europe. 

The  most  noteworthy  instance  of  this  sort  in  America  was  wit- 
nessed by  the  writer  on  Sunday,  December  20th,  1903,  at  Newark,  N.  J., 
when  the  220-ft.  double-deck  draw-bridge  of  the  Delaware,  Lacka- 
wanna and  Western  Railroad,  across  the  Passaic  River,  was  moved, 
complete  and  ready  for  use,  to  its  present  position,  under  the  direc- 
tion of  Lincoln  Bush,  M.  Am.  Soc.  C.  E.,  Chief  Engineer.  The  bridge 
is  center-bearing,  and  has  four  tracks.  It  was  moved  up  stream  some 
40  ft.  and  lowered  10J  ft.  from  its  level  at  the  old  pier. 

Several  years  before,  it  had  become  necessary  to  renew  the  old 
draw,  and  as  grade-crossing  wrork  was  in  progress  in  the  vicinity,  the 
new  draw  was  designed  accordingly,  and  the  lower  deck  used  tem- 
porarily. 

The  weight  of  the  bridge  was  1  017*  tons,  and  the  sand  and  timber- 
work  936  more,  a  total  of  1  953  tons  on  the  scows  above  the  deck. 

A  year  or  so  before,  there  had  been  experiments  on  the  action  of 
sand  in  compression  by  loading  two  83-ft.  girders  on  a  pair  of  plungers 

*  Engineering  News,  Vol.  so,  p.  B06. 


22  REPLACEMENT  OF  THE  HARLEM  SHIP  CANAL  BRIDGE 


fitting  into  4  by  6-ft.  boxes.  It  was  found  that  there  was  little  swelling, 
that  the  most  favorable  angle  of  the  side  holes  was  45°,  and  that 
the  holes  should  be  made  funnel-shaped,  with  a  diameter  of  2  in.  inside 
and  3  in.  outside  the  box.  There  were  also  2-in.  holes  in  the  bottom  of 
the  box.    All  holes  were  regulated  by  slides. 

The  bridge  rested  on  two  scows  under  each  arm,  and  there  were 
four  sand  boxes  of  12  by  12-in.  stuff,  each  52  ft.  long,  12£  ft.  high  and 
about  4  ft.  wide,  inside  measurements.  The  plungers  had  a  clearance 
of  \  in.,  and  their  pressure  on  the  sand  was  less  than- li  tons  per  sq.  ft. 

The  rise  of  tide  at  Newark  is  generally  somewhat  more  than  4  ft. 
but  on  the  day  the  bridge  was  moved  the  wind  and  tide  were  perverse, 
and,  unfortunately,  there  was  a  rain  all  day;  so  that  it  was  with  dif- 
ficulty that  the  sand  was  kept  in  prime  flowing  condition,  tarpaulins 
being  used  to  protect  it  as  much  as  possible. 

In  spite  of  all  precautions,  there  was  irregular  settling,  and  time 
was  lost  in  balancing  the  movement.  The  bridge  had  been  raised  by 
the  tide,  helped  by  four  centrifugal  pumps.  A  boiler  scow  and  pump 
was  held  in  reserve.    The  rate  of  movement  was  as  follows: 

At  0.30  a.  m.,  the  old  supports  were  cleared, 
"  0.35  a.  M.,  began  lowering  at  the  new  site, 
"  5.00  p.  M.,  the  span  rested  on  the  new  pivot, 
.    "  6.15  p.  m.,  all  scows  had  been  released, 
"  8.30  p.  m.,  the  first  train  crossed  over. 

The  objection  to  this  method  is  the  likelihood  of  wetting  the  Band 
(which  in  this  case  was  screened  through  a  sieve  of  \-\w.  mesh)  and  the 
consequent  ignorance  as  to  what  is  going  on  inside  the  boxes.  Under 
such  conditions,  looking  for  evidence  of  strain  in  heavy  timber  is  a 
responsibility  which  few  engineers  would  care  to  take. 

Finally,  other  notation  operations  on  the  Harlem  River  should  be 
mentioned,  namely:  At  Macomb's  Dam  Bridge,  at  Madison  Avenue, 
and  possibly  at  the  crossing  of  the  New  York  Central  and  Hudson 
River  Railroad — operations  which  deserve  to  be  recorded  in  detail. 


DISCISSION   OX    I  f  A  HI.  KM    Mill'  CANAL  HHIlNiK 


DISCUSSION 


Lincoln  Rrsn,  M.  A.m.  Six.  ('.  K.  (by  letter).     In  reference  to  tlie  Mr. 
use  of  sand  jacks  for  lowering  the  draw-bridge  of  the  Delaware,  Lacka-  Bu!,,l 
wanna  and  Western  Railroad  over  the  Passaic  River  at  Newark,  N.  J., 
on  December  20th,  1903,  the  following  comments  are  offered: 

On  the  day  the  bridge  was  moved  and  lowered,  rain  commenced  at 
1.20  a.  IE.,  and  continued  until  5.00  P.  M.,  at  which  time  the  bridge 
rested  on  the  new  center  pier  in  exact  position,  the  precipitation  during 
this  time  being  1.23  in.  In  order  to  keep  the  sand  dry  while  the 
-and  boxes  were  being  filled  and  for  the  same  purpose  after  they 
were  filled,  tarpaulins  had  been  provided  before  the  operation.  During 
the  night  prior  to  the  move,  one  of  the  tarpaulins  accidentally 
became  partly  removed  on  the  south  side  of  one  of  the  four  boxes, 
letting  some  water  into  the  sand  near  the  top  of  the  box.  This  wet 
sand,  however,  caused  a  delay  of  only  20  min.  in  the  lowering,  and, 
aside  from  this  -incident,  there  was  not  the  least  difficulty  in  keeping 
the  sand  dry,  even  with  the  heavy  precipitation  of  1.23  in. 

Mr.  Howe  mentions  the  irregular  settling  and  lost  time  in  balancing 
the  movement.  He  probably  refers  to  the  lowering  of  one  end  of  the 
bridge  at  a  time,  which  was  done  in  2-ft.  stages.  The  day  was  chilly, 
and  the  men  were  wet  to  the  skin.  The  writer  was  reasonably  certain 
that  the  operation  could  be  completed  on  schedule  time,  by  handling 
the  lowering  slowly  and  carefully,  rather  than  by  seeing  how  quickly 
it  could  be  done,  and,  instead  of  lowering  both  ends  of  the  bridge  at 
the  same  time,  he  adopted  the  plan  already  mentioned.  It  was  shown 
l>y  tests  made  with  test  sand  boxes,  and  in  the  actual  lowering  of  the 
bridge  itself,  that  the  bridge  could  be  lowered  very  readily  at  the  rate 
of  3  in.  per  min. 

Observations  on  the  tide  movements  at  the  bridge  site  for  four 
months,  and  other  reliable  data,  showed  that  at  times  the  minimum 
low  tide  did  not  fall  below  zero  or  mean  tide,  and  that  the  maximum 
low  tide  frequently  fell  to  an  elevation  of  3  ft.  below  mean  tide.  These 
data  also  showed  that  at  times  the  high  tide  did  not  go  above  mean 
tide,  and  that  the  maximum  high  tide  at  times  rose  to  a  point  4  ft. 
above  mean  tide.  These  observations  showed  that  the  minimum  varia- 
tion between  high  and  low  tide  was  nothing,  and  that  the  maximum 
variation  was  7  ft.  The  normal  variation  lor  low  tide  at  the  bridge 
site  is  — 2.5  ft.  (below  mean  tide),  and  the  normal  variation  for  high 
tide  is  +2.5  ft.  (above  mean  tide). 

The  work  had  to  be  done,  as  planned,  in  12  hours,  in  other  words, 
from  low  tide  to  low  tide.  When  the  four  barges  were  run  under  the 
bridge,  the  low  tide  was  — 1.0  ft.,  and  when  they  were  released  at  the 
next  low  tide,  fell  to  only  — 1  ft.  instead  of  a  normal  low  tide  of 


24 


DISCUSSION  ON   HABLEM  SHIP  CANAL  BRIDGE 


Mr.  — 2.5  ft.  The  high  tide  rose  to  +3.0  ft.  instead  of  a  normal  high 
Bu8h-  tide  of  +2.5  ft. 

The  tests  made  with  test  sand  boxes  showed,  with  most  convincing 
evidence,  that  dry  sand,  carrying  a  load  of  about  2  500  lb.  per  sq.  ft., 
produced  very  little  lateral  pressure;  and  no  outward  deflection  of  the 
timber,  with  a  straight-edge  on  the  sides  of  the  boxes,  was  discernible. 
Neither  was  there  any  perceptible  deflection  in  the  sides  of  the  timber 
boxes  used  in  lowering  the  bridge,  except  with  one  box  where  wet  sand 
occurred,  and,  as  stated,  this  was  relieved  with  a  delay  of  only  20  min. 
by  opening  the  sand  holes  lower  down  in  the  box  where  dry  sand  flowed 
out  freely.* 

The  fact  that  the  work  was  done  on  schedule  time,  as  planned,  witli 
abnormal  tide  conditions  and  a  heavy  rainfall  continuing  throughout 
the  operation,  should  be  convincing  evidence  that  this  method  of  lower- 
ing a  heavy  structure,  tempered  with  good  judgment,  is  perfectly  safe, 
economical,  and  efficient. 

Mr.      Martin  Gay,  M.  Am.  Soc.  C.  E. — When  the  proposal  was  first  made 
Uay*  to  run  the  trains  of  the  Rapid  Transit  Railroad  across  the  Harlem 
Ship  Canal  Bridge,  it  was  thought  feasible  to  add  an  upper  deck  to 
the  old  draw-span  and  to  build  new  spans  above  the  old  approaches. 

This  was  objected  to  by  the  Department  of  Bridges,  under  the 
jurisdiction  of  which  the  bridge  came,  on  the  ground  that  the  turn- 
table, though  well  designed  and  sufficient  to  carry  its  comparatively 
light  load  of  some  700  tons,  was  not  substantial  enough  to  endure  the 
racking  and  distortions  due  to  a  moving  load  of  perhaps  twice  that 
weight. 

While  this  point  was  under  discussion  by  the  engineers  of  the 
Department  of  Bridges  and  the  Rapid  Transit  Commission,  several 
other  interests  came  into  view.  For  some  years  the  Kingsbridge 
Railroad  Company  had  held  a  franchise  permitting  it  to  cross  the 
bridge,  and  its  officers  had  discussed  the  question  with  sufficient  serious- 
ness to  cause  the  Department  of  Bridges  to  make  a  study  of  the  situa- 
tion and  to  determine  that  it  would  be  necessary  to  strengthen  the 
floor  system  and  practically  rebuild  it  at  a  higher  elevation,  and  also 
to  change  the  grade  of  the  approaching  streets.  This  would  have  been 
a  matter  of  considerable  expense. 

Also,  the  New  York  Central  Railroad,  in  connection  with  the  plait 
for  the  elimination  of  grade  crossings,  had  prepared  to  abandon  the 
long  curve  with  many  crossings  through  Kingsbridge  Village,  and  to 
cross  from  the  east  bank  of  the  Harlem  River  to  the  east  bank  of  the 
Hudson,  following  the  north  bank  of  the  Ship  ('anal  and  passing 
under  the  Ship  Canal  Bridge.    To  do  this  an  additional  space  of  12  ft. 

*An  BOOUrate  and  full  presentation  of  this  Operation  and  the  tests  mad«  prior  to  it 

are  given  in  WngineerinQ  ZVeic*,  December  :i;st.  1906. 


DISCUSSION  ON    II  MM. KM   S 1 1 II '  CANAL  HKIlXiK 


was  required  between  the  bulkhead  of  the  canal  and  the  north  abutment  Mr. 
of  the  bridge.  (iav 

Also,  at  this  time  the  Department  of  Bridges  was  planning  a  new 
bridge  across  the  Harlem,  near  Fordham  Landing,  and  had  about 
determined  to  build  a  double-leaf  rolling  lift  of  the  Scherzer  type. 

It  was  to  the  combination  of  these  various  interests  that  we  owe 
this  admirable  paper.  Each  party  to  the  combination  contributed  its 
share  of  the  cost  of  the  project,  either  in  money  or  in  work,  or  both, 
and  each  got  what  it  wanted. 

Mr.  Howe  has  described  the  work  of  moving  the  bridge  so  clearly 
that  little  can  be  said  on  that  head. 

Each  of  the  six  operations,  that  is,  moving  out  an  old  span  or 
moving  in  a  new  one,  was  not  of  itself  a  very  complex  problem,  but, 
taken  altogether,  it  was  a  work  of  considerable  magnitude,  and  con- 
sidering the  cramped  space  in  which  the  contractor  was  obliged  to 
maneuver  the  approach  spans,  the  uncertainty  of  the  tides,  and  the 
short  space  of  time  during  which  he  could  obstruct  travel,  the  problem 
was  one  requiring  nice  calculation  and  unusual  judgment. 

The  time  during  which  street  travel  could  be  obstructed  was  fixed 
by  the  Department  of  Bridges,  whose  duty  it  was  to  consider  the  con- 
venience of  the  public,  after  consultation  with  Messrs.  Terry  and 
Tench,  as  to  the  methods  they  proposed  to  use  and  the  time  they  would 
require.  The  Department  wras  not  willing  to  deprive  people  of  an 
opportunity  to  cross  the  stream  for  a  longer  time  than  necessary,  and 
did  not  wish  to  impose  oppressive  conditions  on  the  contractors. 

It  was  estimated  that  one  day  would  be  sufficient  to  move  and  re- 
adjust each  of  the  approach  spans,  allowing  for  accidents  and  delays, 
and  that  3  days  would  be  required  for  the  draw-span.  Therefore,  the 
permit  allowed  street  travel  to  be  interrupted  for  a  total  time  of  5  days, 
but  not  for  more  than  3  days  consecutively.  That  no  very  serious 
delays  occurred  is  indicated  by  an  analysis  of  Mr.  ITowe's  figures, 
which  shows  that  the  total  time  of  interrupted  travel  was  3  days,  1C 
hours,  35  min.,  and  that  during  the  moving  of  the  draw-span,  tin 
interruption  was  less  than  the  stipulated  3  days  by  4  hours,  55  min. 

Each  of  the  three  new  spans  was  put  to  use  by  vehicles  and  pedes 
trians  as  soon  as  it  was  placed  in  position,  and  the  draw-span  was 
opened  to  pass  vessels  without  causing  any  delay  to  river  traffic. 

The  old  spans,  which  have  become  a  part  of  the  University  Heights 
Bridge,  had  to  have  considerable  changes  in  order  to  bring  them  up  t«> 
modern  requirements,  and  they  have  done  duty  continuously  since  the 
formal  opening  of  the  bridge. 

In  all  operations  of  this  nature  on  the  Harlem  River,  of  which 
there  is  any  record,  the  rise  and  fall  of  the  tide  has  been  counted  on 
as  a  factor  and  has  been  used  to  some  purpose,  and  yet  it  is  such  an 
uncertain  factor  thai  in  almost  every  case,  other  means  for  raising  or 


2G 


DLSCL'SSION   ON    FIAIM.KM    SIII1*  CANAL  BKIIXJK 


Mr.  lowering-  have  been  provided  and  usually  resorted  to,  in  order  to 
'  supplement  the  deficiency  of  tidal  power.  As  the  movements  of  the 
tides,  of  greater  or  less  extent,  take  place  at  more  or  less  definitely 
known  times,  they  must  be  reckoned  with.  On  a  non-tidal  stream, 
however,  where  other  power  would  of  necessity  be  provided,  the  attend- 
ant uncertainty  and  anxiety  regarding  the  behavior  of  the  tide  would 
be  eliminated,  and  probably  the  cost  would  not  be  greatly  increased. 

One  occasion  on  which  the  lifting  power  of  the  tide  was  used  to 
good  advantage,  but  perhaps  not  with  any  great  economy,  was  in  the 
moving  of  the  draw-span  of  the  old  Macomb's  Dam  Bridge,  of  which 
Mr.  Howe  has  spoken.  The  bridge  was  built  in  the  early  Sixties,  and 
was  replaced  in  1892  by  the  present  structure,  which  was  designed 
and  the  construction  supervised  by  A.  P.  Boiler,  M.  Am.  Soc.  C.  E. 
It  was  necessary  to  remove  the  old  bridge  to  make  way  for  the  new 
one,  and  it  was  also  necessary  to  provide  for  public  travel.  It  was 
decided,  therefore,  to  move  the  draw  one  block  north  of  the  old  site,  to 
the  line  of  15Gth  Street.  A  pivot  pier  and  approaches  having  been 
constructed  at  an  elevation  12  ft.  lower  than  that  of  the  bridge,  the 
problem  was  to  move  the  draw-span  about  200  ft.  north,  and  to  lower 
it  12  ft.  to  its  new  position  without  obstructing  navigation.  This  was 
done  by  lifting  the  span  on  two  scows  and  a  cribbing  of  12  by  12-in. 
timbers,  and  towing  it  to  a  pile  and  cribbing  pier  which  had  been  built 
near  the  bank  of  the  stream  and  out  of  the  course  of  passing  vessels. 

Here  it  was  deposited  safely  at  an  elevation  somewhat  lower  than 
that  from  which  it  had  started.  When  the  next  flood  tide  raised  the 
scows  and  bridge,  a  course  of  crib  timbers  was  pulled  off  the  pier,  and 
as  the  span  settled  with  the  ebb  tide  and  rested,  a  course  of  crib 
timbers  was  taken  off  the  scows.  As  the  next  flood  tide  freed  the  span 
from  the  pier,  another  course  of  timbers  was  removed  and  so  on,  until 
it  rested  at  the  proper  elevation  to  be  floated  across  to  the  permanent 
pier  and  be  placed  in  position. 

An  instance  of  the  tide  not  doing  its  duty,  as  expected,  was  at  the 
moving  of  the  Madison  Avenue  draw-span,  where  an  east  storm  made 
an  early  flood  which  caught  and  held  the  scows  under  the  span  after 
it  had  been  landed.  Considerable  damage  might  have  resulted,  but 
for  the  scuttling  of  one  of  the  scows. 

Mr.         St.  John  Clarke,  M.  Am.  Soc.  C.  E. — As  Mr.  Gay  lias  mentioned 
laik<>'  a  design  prepared  for  this  bridge,  in  which  parts  of  the  old  bridge 
were  used,  it  may  be  of  interest  to  explain  more  fully  the  reason  for 
making  this  design. 

When  the  crossing  of  the  Harlem  at  this  point  was  being  con- 
sidered by  the  engineers  of  the  Rapid  Transit  Commission,  it  developed 
tlnit  the  Bridge  Department  desired  a  wider  bridge,  and  also  wanted 
to  use  the  old  bridge  at  the  lower  crossing;  that  the  New  York  Central 
wanted  to  change  the  northern  span,  so  as  to  give  more1  head-room 


DISCUSSION  OX   HARLEM  SHIP  CANAL  BRIDGE 


27 


and  also  room  for  more  tracks;  and  that  the  Metropolitan  Street  Rail-  Mr. 
way  Company  was  considering  a  change  in  the  floor  system  of  the  old 
bridge,  so  as  to  provide  a  slot  and  conduit  in  order  to  allow  the  surface 
cars  to  cross  the  bridge  and  continue  up  Broadway.  Changes  in  the 
old  bridge  for  any  one  of  these  interests  would  have  been  quite 
expensive;  but  to  provide  for  these  several  requirements  in  a  new 
bridge  would  not  add  very  materially  to  its  cost. 

The  stand  was  taken  by  the  other  interests  that  the  Rapid  Transit 
Commission,  or  rather  its  contractor,  had  to  build  a  new  bridge  in  any 
case,  and  that,  while  doing  so,  it  would  be  better  to  provide  for  all 
future  uses  of  the  bridge,  the  additional  cost  being  small.  It  is  hardly 
necessary  to  add  that  these  interests  displayed  no  great  willingness  to 
assume  a  fair  share  in  the  cost  of  the  new  bridge. 

It  was  because  of  this  condition  of  affairs  that  the  speaker,  as 
General  Inspector  of  Designs,  considered  the  possibility  of  using  the 
old  bridge.  A  design  was  prepared  utilizing  the  floor  system,  turn- 
table, and  machinery,  with  the  bottom  chord  of  the  old  draw,  new 
and  deeper  trusses  being  provided.  This  design  complied  with  all 
the  theoretical  requirements  of  the  Bridge  Department,  and  it  was 
shown  that  the  old  bridge  could  be  altered  to  serve  the  Rapid  Transit 
Railroad.  When  this  was  evident,  and  not  before,  it  became  possible 
to  make  a  fair  arrangement  with  the  various  interests  involved.  The 
new  bridge  was  designed,  and  all  those  using  it  contributed  to  the  cost. 

All  were  somewhat  disappointed  because  the  design  for  using  the 
old  bridge  was  not  adopted,  as  it  seemed  hardly  fair  to  these  plans 
after  they  had  served  their  purpose  so  well. 

Theodore  Belzner,  Jun.  Am.  Soc.  C.  E.  (by  letter). — The  writer  Mr. 
was  connected  with  the  construction  of  this  bridge  as  Inspector  of  Belzne 
Erection,  for  the  Rapid  Transit  Railroad  Commission,  and  recalls  the 
cracks  which  were  discovered  at  the  apex  of  the  connecting  angle 
plates,  and  during  the  riveting  up  of  those  replaced.  In  a  general  way, 
he  tested  the  shop  rivets  of  the  connecting  plates  at  the  other  end  of  the 
pivot  girder,  in  order  to  determine  their  tightness  as  compared  with  the 
field-driven  rivets,  and  found  quite  a  number  of  the  shop  rivets  loose. 
This  was  reported  to  Mr.  Howe,  and  resulted  in  a  conference  between 
the  engineers  and  inspectors.  It  was  finally  decided  to  cut  off  a  few 
rivet  heads  and  drill  out  the  shanks.  This  method  of  removal,  however, 
was  abandoned  after  a  few  rivets  had  been  partially  drilled  out,  as  it 
was  slow  and  costly,  and  in  some  cases  it  was  difficult  to  keep  the  drill 
centered  on  the  rivets,  especially  on  the  innermost  ones.  Then  the 
rivets  were  "backed  out"  and  with  much  better  results,  on  account  of 
the  reamed  holes  in  the  plates,  etc. 

On  May  15th,  190G,  the  writer  reported  the  results  of  lii-  examina- 
tion to  Mr.  Howe,  which  in  part  was  as  follows:* 

*  Transactions,  Am.  Soc.  C.  E.,  Vol.  LVII,  p.  a62. 


DISCUSSION  OX  HARLEM  SHIP  CANAL  BRIDGE 


Mr.  ''The  bent  plate  of  this  member  contained  87  long  1-in.  shop  rivets, 
iezner.  28  0f  which  were  condemned  for  looseness.  The  shop  rivets  were  cut 
out  and  replaced  by  machine-driven  field  rivets.  In  cutting  off  the 
heads  and  'backing  out'  the  rivets,  no  material  damage  was  done  to  the 
adjacent  ones,  but  many  of  them  became  loosened  while  the  field  rivets 
were  being  driven.  The  rivets  'backed  out'  easily,  some  requiring  only 
a  few  blows  with  an  8-lb.  hammer.  An  examination  of  these  rivets 
showed  that  they  had  not  been  upset  properly,  in  some  cases  shoulders 
were  formed  under  the  heads  (caused  by  oval-shaped  holes  through  the 
bent  plates),  in  other  cases  the  rivets  were  slightly  rusted  and  showed 
some  scale.  The  result  was  that  more  than  60  field  rivets  had  to  be 
driven  to  replace  the  shop  rivets." 

Referring  to  the  twisting  of  the  shafting  of  the  New  Ship  Canal 
Bridge,  the  writer  would  like  to  ask  if  this  occurred  in  driving  home 
the  wedges  on  the  rest  piers? 

If  the  writer  remembers  correctly,  there  was  a  slight  "tilt"  at  the 
southeast  corner  of  the  bridge,  and  some  difficulty  in  driving  the 
wedges,  especially  at  this  point.  Information  as  to  the  adjustment  of 
this  matter  would  be  of  interest. 

How  does  the  efficiency  of  the  shaft  claw  couplings  compare  with 
that  of  the  flanged  ones? 
Mr.  Frank  W.  Skinner,  M.  Am.  Soc.  C.  E.  (by  letter). — The  opera- 
1  ner"  tions  described  in  this  paper  are  nearly  or  quite  the  most  intricate 
and  prolonged  of  any  of  similar  character  yet  effected,  and  their 
complete  success  under  difficult  and  involved  conditions  reflects  great 
credit  on  the  engineers  and  contractors  for  the  preparation  of  the 
plans  and  for  their  courage  and  ability  in  executing  them. 

The  author's  description  of  the  moving  of  this  bridge  is  so  com- 
plete that  there  is  no  room  for  criticism  or  discussion,  but  some  addi- 
tional facts  concerning  other  work  of  a  similar  nature  which  he 
mentioned  briefly,  may  be  timely. 

The  Hawkesbury  Bridge,  Australia,  has  seven  through,  double-track 
spans  which  were  erected  successively  on  falsework,  34  ft.  high,  on  the 
deck  of  a  Gl  by  335-ft  pontoon,  10  ft.  deep,  stiffened  by  bulkheads  and 
trussing  cables,  and  sunk  on  a  timber  grillage  in  shallow  water.  After 
the  completion  of  each  span,  the  water  was  drained  out  of  the  pontoon 
at  low  tide,  and  at  high  tide  it  was  hauled  to  the  piers,  a  distance  of 
about  4  000  ft.,  by  two  cables  operated  by  fixed  hoisting  engines.  Bach 
span  was  lowered  to  the  piers  by  admitting  water  ballast  to  the  pon- 
toon. Despite  several  accidents,  such  as  the  breaking  of  the  cables, 
the  grounding  of  the  pontoon,  and  the  reversing  of  one  span,  the  erec- 
tion was  accomplished  successfully. 

The  single-track  bridge  across  two  branches  of  the  Miramichi 
River,  New  Brunswick,  had  twelve  204-ft.  -pans,  each  weighing  about 
225  ton-.  Without  much  interruption  of  t  ratlic,  these  were  replaced. 
i.ii  the  same  piers,  by  stronger  270-ton  spans.    Two  Beta  of  pile  false- 


PLATE  IV. 
TRANS.  AM.  SOC.  ClV.  ENGRS. 
VOL.  LXVII,  No.  1143. 
SKINNER  ON 
HARLEM  SHIP  CANAL  BRIDGE. 


Fig.  2. — Brcnot  Island  Briikjk  Across  thk  Ohio  Hivkh.   Completed  Span  and 
Falsework  Floated  on  Ni>e  Hahges. 


DISCUSSION  ON    HARLEM  SHIP  CANAL  BRIDGE 


2!) 


work,  opposite  each  other,  were  established  parallel  and  close  to  the 

old  bridge,  and  the  new  spans  were  creeled  successively  on  one  of  them, 
skidded  across  to  the  other,  and  riveted  up  while  the  next  span  was 
being  erected  on  the  first  falsework.  After  the  riveting  was  com- 
pleted the  span  was  transferred  to  towers  on  the  decks  of  a  pair  of 
pontoons,  and  was  towed  to  position  between  the  piers.  Simultane- 
ously, the  old  span  was  lifted  from  its  piers  and  removed  on  a  Howe 
truss  span  on  the  decks  of  two  other  pontoons.  In  some  cases  the  old 
spans  were  deposited  on  trucks  on  falsework,  rolled  ashore,  and  dis- 
mantled at  leisure;  in  other  cases  they  were  deposited  on  piles  driven 
in  the  river  and  there  taken  apart  with  an  ordinary  traveler.  The 
spans  were  replaced  with  an  average  interruption  of  traffic  of  about 
4  hours. 

The  Coteau  Bridge,  across  the  St.  Lawrence  River,  has  14  spans 
about  220  ft.  long.  These  were  erected  successively  on  shore  false- 
work about  3  miles  up  stream  from  the  site,  skidded  to  towers  on  the 
decks  of  a  pair  of  pontoons  trussed  together,  safely  towed  down  through 
a  7-mile  current,  and  deposited  on  their  piers. 

The  Midland  Railway  crosses  the  Shubenacadie  River,  Nova  Scotia, 
at  a  point  where  it  is  subject  to  a  32-ft.  rise  of  the  tide.  The  current 
is  very  swift,  and  the  bottom  under  three  of  the  215-ft.,  330  000-lb.  pin- 
connected-truss  through  spans  was  too  soft  to  support  falsework;  there- 
fore these  spans  were  erected  on  pile  falsework  at  right  angles  to  the 
bridge  axis,  transferred  to  towers  on  a  pair  of  pontoons,  and  hauled  to 
position  by.  hoisting  engines  located  on  the  bridge  piers.  Each  span  was 
transferred  from  the  falsework  to  its  permanent  position  in  less  than 
2  hours. 

The  232-ft.  span  of  the  Fraser  River  Bridge,  at  New  Westminster, 
British  Columbia,  has  two  trusses  54  ft.  deep,  20  ft.  apart  at  one  end 
and  135£  ft.  apart,  at  the  other.  These  were  erected  successively  on 
falsework  in  the  river  near  a  completed  span  of  the  bridge.  The  first 
truss  was  moved  transversely  to  a  temporary  support  on  falsework 
piers,  and  the  second  truss  was  erected  and  braced  to  it;  the  heavy 
floor-beams  and  transverse  struts  were  assembled,  and  the  468-ton  span 
was  transferred  to  three  large  pontoons,  floated  on  them  to  position, 
and  lowered  to  its  bearing  on  its  three  permanent  piers. 

Other  bridges  floated  to  position  in  America,  are  the  Belle  [sle 
Bridge,  Detroit,  eleven  156-ft.  spans  of  which  were  erected  on  shore 
and  towed  nearly  a  mile  to  the  site;  several  draw-bridges;  and  the 
Harvard  Bridge,  Boston,  -with  23  spans  ranging  from  76  to  106  ft., 
the  separate  girders  of  which  were  delivered  by  a  gantry  crane  to  a 
large  scow,  towed,  to  position,  and  lowered  to  their  piers  by  admitting 
water  ballast  and  by  the  falling  tide. 

The  anchor  arm  of  the  long-span  Tnterprovincial  Bridge,  across  the 
Ottawa  River,  and  the  Faidherbo  Bridge,  in   Africa,  were  ereccted 


DISCUSSION  ON  HARLEM  SHIP  CANAL  BRIDGE 


Mr^    od  falsework  supported  on  boats,  and  the  Bismarck,  Omaha,  and  Glas- 
'  gow  Bridges,  across  the  Missouri  River,  were  all  erected  or  replaced 
on  falsework  trusses  which  were  moved  from  pier  to  pier  on  pontoons. 

HMr.^       Horace  J.  Howe,  M.  Am.  Soc.  C.  E.  (by  letter).— In  comparing 
'  old  and  new  methods,  the  advance  is  found  to  be  along  these  lines: 
First. — The  use  of  well-bonded  cribbing,  in  preference  to  framed 
bents  on  the  scows; 

Second. — The  supply  of  abundant  steam  for  pumping  water  in  and 
out  of  the  scows,  thereby  neutralizing  any  uncertainty  as  to  the  tide; 
Third. — The  use  of  tugs  of  ordinary  size; 

Fourth. — The  use  of  improved  hydraulic  jacks  or  presses,  for 
adjustments; 

Fifth. — The  use  of  sand  jacks  for  loads  of  2  000  tons  or  more,  under 
particular  circumstances. 

The  writer  thinks  that  much  might  have  been  said  in  the  dis- 
cussion as  to  the  last  two  headings. 

When  one  calculates  the  cost  of  the  time  frequently  wasted  by  a 
high-priced  gang  of  men,  on  account  of  defective  judgment  as  to 
jacks,  and  compares  this  cost  with  the  rental  of  adequate  power,  he  is 
led  to  think  that  here  is  a  new  field  for  the  engineer. 

Mr.  Bush  has  taken  a  step  ahead,  in  this  respect.  He  also  is  in 
line  with  Mr.  Stephenson  and  others  in  informing  himself  by  previous 
experiments  on  a  generous  scale  of  what  might  reasonably  be  ex- 
pected; and  furthermore,  in  allowing  generously  for  contingencies  of 
all  kinds  during  the  critical  period. 

Mr.  Gay's  experience  with  the  Harlem,  and  his  proximity  to  the 
work  described,  render  his  opinions  of  especial  value.  His  estimate 
of  the  loss  of  time  to  the  traveling  public  at  the  bridge  proved  to  bo 
nearly  exact. 

Mr.  Clarke's  design,  it  is  needless  to  say,  involved  expert  work  of 
a  high  order.  As  one  examines  the  bridge  to-day,  he  is  struck  with 
its  difficulties,  and  furthermore  of  the  subsequent  difficulties  of  im- 
pressing opposing  interests  as  to  its  practicability. 

The  writer  would  call  Mr.  Belzner's  attention  to  the  quality  of 
I  he  hand  riveting  of  Mr.  Stephenson's  time,  superseding,  in  fact,  the 
steam  riveting  at  Conway. 

To-day,  it  would  be  quite  a  question  bow  long  it  would  take  a 
power-riveter  to  become  as  truly  expert  at  hand-riveting  as  one  of  those 
<»ld-t  imo  riveters.  Attention  is  also  called  to  the  avoidance  of  painting 
the  plates  before  riveting,  and  the  use  of  red  and  white  lead  as  a  filler, 
both  practices  being  in  line  with  the  writer's  experience. 

As  to  the  twisted  shafting,  probably  more  work  was  done  at  that 
corner  by  the  wedges,  in  lifting  the  bridge,  due  to  slowness  of  action 
relative  to  the  other  wedges.    The  bridge  seats  are  known  to  be  level. 


DISCISSION  <>\    IIAKLKM   BHIP  CANAL  BRIDGE 


31 


The  writer  is  informed  that  the  "clutch"  couplings  have  worked  :\ir 
satisfactorily.     On  a  draw-bridge  subject  to  deflections  and  vibra-  How' 
tions,  there  seems  to  be  a  certain  amount  of  "give"  necessary  to  a  line 
of  shafting. 

The  writer  is  indebted  to  Mr.  Skinner  for  his  illustration  of  the 
classic  falsework  used  at  the  Brunot  Island  Bridge,  and  for  his  other 
references,  bringing  the  subject  substantially  up  to  date. 


AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS 

INSTITUTED  1852 


TRANSACTIONS 


Paper  No.  1144 

PRECARIOUS  EXPEDIENTS  IN  ENGINEERING 
PRACTICE.* 

By  John  Hawkesvvorth,  Assoc.  M.  Am.  Soc.  C.  E. 

With  Discussion  hy  Mi-msrk.  Elcknk  W.  Stkrw  W.  W.  Crosby,  J.  S. 
Branne,  Andrews  Allen,  Guy  B.  Watte,  J.  H. 
GandolpOj  ind  John  Hawkesworth. 


In  presenting  this  paper  for  the  Society's  consideration,  the  obser- 
vation may  be  made  that  it  is  not,  in  the  strict  sense  of  the  term,  a 
scientific  paper.  It  would  seem,  however,  that  if  engineers  h?d  no 
thoughts  or  aspirations  in  regard  to  their  Profession,  other  than  those 
applying  to  technical  details,  that  Profession,  and  the  Society  which 
represents  it,  would  fall  short  of  the  standards  which  inspire  workers 
in  other  fields.  In  the  many  scientific  papers  which  are  continually 
being  presented,  attention  is  directed  to  methods  and  formulas  by 
which  one  may  build  safely  and  efficiently.  With  these  two  watch- 
words of  the  Engineering  Profession — "safety"  and  "efficiency" — is 
it  not  necessary  to  class  the  additional  word,  "honesty"?  In  the 
Engineering  Profession,  as  in  other  professions,  ordinary  intentional 
dishonesty  sooner  or  later  brings  its  own  punishment.  It  is  not  to 
such  self-evident  facts  that  the  writer  would  draw  attention. 

I  nere  is  another  kind  of  dishonesty  to  which  one  may,  without 
premeditation,  be  made  accessory,  which  is  known  to  every  engineer 
and  architect,  yet  very  rarely  discussed.  Possibly  this  is  because  some 
may  believe  it  is  the  result  of  the  present  method  of  financing  large 

*  Presented  at  the  nieetinc  of  February  18th,  1&10. 


